完整托福模拟题阅读

1、最新完整托福模拟题阅读(一一)Questio ns 12-20 The eleme nts other tha n hydroge n and helium exist In such small qua ntities that it is accurate to say that the uni verse somewhat more tha n 25 perce nt helium by weight and somewhat less tha n 25 perce nt hydroge n. Astr ono mers hQuestio ns 12-20The eleme nts ot

2、her tha n hydroge n and helium exist In such small qua ntities that it is accurate to say that the uni verse somewhat more tha n 25 perce nt helium by weight and somewhat less tha n 25 perce nt hydroge n.Astrono mers have measured the abundance of helium throughout our galaxy and in other galaxies a

3、s well. Helium has bee n found In old stars, in relatively young on es, in interstellar gas, and in the distant objects known as quasars. Helium nuclei have also bee n found to be con stitue nts of cosmic rays that fall on the earth (cosmic rays are n ot really a form of radiati on; they con sist of

4、 rapidly movi ng particles of nu merous differe nt kin ds). It does nt seem to make very much differe nee where the helium is foun d. Its relative abundance n ever seems to vary much. In some places, there may be slightly more of it; In others, slightly less, but the ratio of helium to hydroge n nu

5、clei always rema ins about the same.Helium is created in stars. In fact, nuclear reactions that convert hydrogen to helium are resp on sible for most of the en ergy that stars produce. However, the amount of helium that could have bee n produced in this manner can be calculated, and it tur ns out to

6、 be no more tha n a few perce nt. The uni verse has not existed long eno ugh for this figure to he sig nifica ntly greater. Con seque ntly, if the uni verse is somewhat more tha n 25 perce nt helium now, the n it must have bee n about 25 perce nt helium at a time n ear the beg innin g.However, whe n

7、 the uni verse was less tha n one min ute old, no helium could have existed. Calculati ons in dicate that before this time temperatures were too high and particles of matter were moving around much too rapidly. It was only after the one-minute point that helium could exist. By this time, the univers

8、e had cooled sufficie ntly that n eutr ons and prot ons could stick together. But the nuclear reactions that led to the formation of helium went on for only a relatively short time. By the time the uni verse was a few mi nu tes old, helium producti on had effectively ceased.what does the passage mai

9、nly expla in?How stars produce en ergyThe differe nee betwee n helium and hydroge nWhe n most of the helium in the uni verse was formedWhy hydroge n is abundantAccord ing to the passage, helium isthe sec on d-most abundant eleme nt in the uni versedifficult to detectthe oldest eleme nt in the uni ve

10、rsethe most prevale nt eleme nt in quasarsThe word con stitue nts in line 7 is closest in meaning to(A) relatives (B) causes (C)comp onents (D) targetsWhy does the author mention cosmic rayst in line 7?As part of a list of things containing heliumAs an example of an un solved astr ono mical puzzleTo

11、 expla in how the uni verse bega nTo expla in the abundance of hydroge n in the uni verseThe word vary in line 10 is closest ill meaning to(A) mea n (B) stretch (C) cha nge(D) in cludeThe creation of helium within stars (A) cannot be measured (B) produces en ergyproduces hydroge n as a by-productcau

12、ses helium to be much more abundant In old stars tha n In young star:The word calculated in line 15 is closest in meaning to(A) ignored (B) conv erted (C) in creased (D) determ inedMost of the helium in the uni verse was formedin in terstellar space (B) in a very short timeduri ng the first mi nute

13、of the uni verses existe ncebefore most of the hydroge nThe word ceased in line 26 is closest in meaning to(A)exte nded (B)performed(C)take n hold (D)stoppedHormones in the BodyUp to the begi nning of the twen tieth cen tury, the n ervous system was thought to con trol all com muni catio n with in t

14、he body and the result ing in tegrati on of behavior. Scientists had determined that nerves ran, essentially, on electrical impulses. These impulses were thought to be the engine for thought, emoti on, moveme nt, and internal processes such as digestio n. However, experime nts by William Bayliss and

15、 Ern est Starling on the chemical secretin, which is produced in the small intestine when food en ters the stomach, eve ntually challe nged that view. From the small in test ine, secret in travels through the bloodstream to the pan creas. There, it stimulates the release of digestive chemicals. In t

16、his fashi on, the in test inal cells that produce secret in ultimately regulate the production of different chemicals in a different organ, the pan creas.Such a coord in ati on of processes had bee n thought to require con trol by the n ervous system; Bayliss and Starl ing showed that it could occur

17、 through chemicals alone. This discovery spurred Starling to coin the term hormone to refer to secretin, taking it from the Greek word hormon, meaning to excite “ or to set in motion.horm one is a chemical produced by one tissue to make thi ngs happe n elsewhere.As more horm ones were discovered, th

18、ey were categorized, primarily accord ing to the process by which they operated on the body. Some glands (which make up the en docri ne system) secrete horm ones directly into the bloodstream. Such gla nds include the thyroid and the pituitary. The exocrine system consists of organs and gla nds that

19、 produce substa nces that are used outside the bloodstream, primarily for digestion. The pancreas is one such organ, although it secretes some chemicals into the blood and thus is also part of the en docri ne system.Much has bee n lear ned about horm ones since their discovery. Some play such key ro

20、les in regulati ng bodily processes or behavior that their abse nee would cause immediate death. The most abundant horm ones have effects that are less obviously urge nt but can be more far-reach ing and difficult to track: They modify moods and affect huma n behavior, eve n some behavior we no rmal

21、ly think of as volun tary. Hormonal systems are very in tricate. Eve n mi nute amounts of the right chemicals can suppress appetite, calm aggressi on, and cha nge the attitude of a pare nt toward a child.Certai n horm ones accelerate the developme nt of the b0dy, regu1at ing growth and form;naistics

22、. The quantities andothers may eve n defi ne an in dividual proporti ons of horm ones produced cha nge with age, so scie ntists have give n a great deal of study to shifts in the endocrine system over time in the hopes of alleviating ailme nts associated with aging.In fact, some horm one therapies a

23、re already very com mon. A comb in ati on of estroge n and progester one has bee n prescribed for decades to wome n who want to reduce mood swin gs, sudde n cha nges in body temperature, and other discomforts caused by lower n atural levels of those horm ones as they en ter middle age. Known as horm

24、 one replaceme nt therapy (HRT), the treatme nt was also believed to preve nt weake ning of the bon es. At least one study has lin ked HRT with a heighte ned risk of heart disease and certa in types of can cer. HRT may also in crease the likelihood that blood clots - dan gerous because they could tr

25、avel through the bloodstream and block major blood vessels will form. Some prop onents of HRT have tempered their enthusiasm in the face of this new evidenee, recommending it only to patients whose symptoms in terfere with their abilities to live no rmal lives.Huma n growth horm one may also be give

26、 n to patie nts who are secreti ng abno rmally low amounts on their own. Because of the complicated effects growth horm one has on the body, such treatme nts are gen erally restricted to childre n who would be pathologically small in stature without it. Growth hormone affects not just physical size

27、but also the digesti on of food and the aging process. Researchers andfamily physicians tend to agree that it is foolhardy to dispense it in cases in which the risks are not clearly outweighed by the ben efits.The word engine in the passage is closest in meaning to(A) desire (B) origi n(C) scie nee

28、(D) chemicalThe word it in the passage refers to(A) secreti n (B) small in testi ne (C) bloodstream (D) pan creasThe word spurred in the passage is closest in meaning to(A) remembered (B) surprised (C) inven ted(D) motivatedTo be con sidered a horm one, a chemical produced in the body mustbe part of

29、 the digestive processin flue nee the operatio ns of the n ervous systemaffect processes in a differe nt part of the bodyregulate attitudes and behaviorThe gla nds and orga ns men ti oned in paragraph 3 are categorized accordi ng towhether scie ntists un dersta nd their fun cti onhow freque ntly the

30、y release horm ones into the bodywhether the horm ones they secrete in flue nee the aging processwhether they secrete chemicals into the bloodParagraph 3 is marked with an arrow -The word key in the passage is closest in meaning to(A) misun derstood (B) precise (C) sig nifica nt (D) simpleThe word m

31、inute in the passage is closest in mea ning to(A) sudden (B) small (C) changing (D) n oticeableWhich of the sen ten ces below best expresses the esse ntial in formatio n in the highlighted sentence in the passage? In correct an swer choices cha nge the meaning in importa nt ways or leave out esse nt

32、ial in formati on.Most moods and acti ons are not volun tary because they are actually produced by the producti on of horm ones in the body.Because the effects of horm ones are difficult to measure, scie ntists rema in un sure how far-reachi ng their effects on moods and actions are.Whe n the body i

33、s not produci ng eno ugh horm on es, urge nt treatme nt may be n ecessary to avoid psychological damage.The in flue nce of many horm ones is not easy to measure, but they can affect both people s psychology and actions extensively.The word tempered in the passage is closest in meaning to(A) decrease

34、d (B) advertised (C) prescribed (D) researchedWhich patie nts are usually treated with growth horm one?Adults of smaller statue tha n no rmalAdults with stro ng digestive systemsChildre n who are not at risk from the treatme ntChildre n who may rema in abno rmally smallWhich of the followi ng senten

35、 ces expla ins the primary goal of horm one replaceme nt therapy?These senten ces are highlighted in the passage.The qua ntities and proporti ons of horm ones produced cha nge with age, so scientists have given a great deal of study to shifts in the endocrine system over time in the hopes of allevia

36、t ing ailme nts associated with aging.A comb in ati on of estroge n and progester one has bee n prescribed for decades to wome n who want to reduce mood swin gs, sudde n cha nges in body temperature, and other discomforts caused by lower n atural levels of those horm ones as they en ter middle age.H

37、RT may also in crease the likelihood that blood clot - dan gerous because they could travel through the bloodstream and block major blood vesselwill form.Because of the complicated effects growth horm one has on the body, such treatme nts are gen erally restricted to childre n who would be pathologi

38、cally small in stature without it.Look at the four squares that indicate where the following sentence could be added to the passage.The body is a complex machi ne, however, and rece nt studies have called into question the wisdom of essentially trying to fool its systems into believing they aren t aging.Where would the sentence best fit?Click on a square to add the sentence to the passage.Directi ons: An in troductory sentence for a brief summary of the passage is provided below. Complete the summary by selecti ng the THREE an swer choices that express the most importa n