An adult giraffe's head is about six feet above its heart. This means that to 36 enough blood up to the brain the circulatory 37 must be strong enough to keep the blood at very high pressure.

　　Biologists have known for some time that giraffes solve this problem by having 38 high blood pressure, about 39 that of human beings. But an international team of biologists began to 40 about this. If giraffes have such high blood pressure, they should have a 41 problem with swelling in their legs and feet. Why don’t giraffes have swollen feet?

　　Giraffes should have 42 problem, too. Every time they bend heads 43 to drink, the blood should 44 to their heads and have a hard time 45 back up (when the head is down) to the heart. How come giraffes don't black out when they drink?

　　The answer to the 46 feet problem, the researchers found, is that giraffes have 47 the researchers call a “natural anti-gravity suit”. It 48 out that the skin and other 49 in their legs and feet are 50 stiffer and tougher than those of other 51 . As a result, the blood vessels in the leg cannot swell.

　　Therefore, the blood has nowhere to go but back to the heart. What about blood rushing to the head 52 the giraffe bends down to drink? The researchers found that the giraffe’s jugular vein, which 53 blood from the head back to the heart, has lots of one-way valves in it. In the giraffe’s neck, there are lots of muscles that flex and relax repeatedly as the animal moves its head and sucks 54 drinking water. By squeezing the valve jugular vein, they 55 blood moving back to the heart even while the animal is drinking.

　　36. A. bring B. produce C. transfer D. pump

　　37. A. structure B. system C. function D. organism

　　38. A. unusually B. generally C. uncomfortably D. commonly

　　39. A. half B. multiple C. double D. pair

　　40. A. investigate B. wonder C. undertake D. learn

　　41. A. terrible B. unreliable C. unsolvable D. advisable

　　42. A. other B. some C. others D. another

　　43. A. up B. down C. toward D. aside

　　44. A. crush B. brush C. push D. rush

　　45. A. following B. returning C. plowing D. pouring

　　46. A. healthy B. swollen C. dreary D. radical

　　47. A. what B. where C. that D. those

　　48. A. reveals B. indicates C. figures D. turns

　　49. A. tissues B. vessels C. pores D. organs

　　50. A. many B. very C. much D. less

　　51. A. giraffes B. animals C. people D. creatures

　　52. A. whenever B. whatever C. however D. wherever

　　53. A. reflects B. releases C. receives D. carries

　　54. A. in B. up C. to D. from

　　55. A. permit B. prevent C. retain D. keep

　　答案解析：

　　36. D

　　詞義辨析題。文章第一句就指出，成年長(zhǎng)頸鹿的腦袋在心臟以上6英尺高的地方�？崭袼�在句子意為“這意味著，要________足夠的血液到大腦，循環(huán)________必須足夠強(qiáng)壯才能保持血液有很強(qiáng)的壓力�！眕ump除了表示“用泵抽”之意，還可以表示“(用泵拉取)注入”，符合句意，所以D正確。

　　37. B

　　詞義辨析題。由空格所在句意可知，空格處是指長(zhǎng)頸鹿的循環(huán)系統(tǒng)，所以B正確。

　　38. A

　　詞義辨析題�？崭袼�在句意為“生物學(xué)家已經(jīng)發(fā)現(xiàn)長(zhǎng)頸鹿有________很高的血壓能解決這個(gè)問(wèn)題”。由此可知，這個(gè)很高的血壓應(yīng)該是與眾不同的，所以A正確。

　　39. C

　　詞義辨析題。根據(jù)空格前面句子意思可知，空格處應(yīng)該是一個(gè)表示倍數(shù)的詞。double是名詞，意為“兩倍”，符合句意，所以選C。前面提到長(zhǎng)頸鹿的血壓很高，所以排除A;multiple只是指“倍數(shù)，若干”，但是沒(méi)有說(shuō)明是多少倍，所以排除。

　　40. B

　　詞義辨析題。空格所在句子句首的but表示轉(zhuǎn)折，說(shuō)明句子內(nèi)容與前面提到的內(nèi)容不同，選項(xiàng)中只有wonder一詞可以表達(dá)這種不同，即“一個(gè)國(guó)際生物學(xué)家小組對(duì)此表示懷疑”，所以B正確。

　　41. A

　　詞義辨析題�？崭袼�在的句意為“如果長(zhǎng)頸鹿的血壓有這么高，那么它們會(huì)有________的問(wèn)題”。選項(xiàng)中terrible意為“很糟糕的”，unreliable意為“不可靠的”，unsolvable意為“不能解決的”，advisable意為“可取的”，只有terrible符合句意，所以A正確。

　　42. D

　　詞義辨析題。通讀第三段可知，該段是在講長(zhǎng)頸鹿血壓很高的話為什么喝水時(shí)不會(huì)暈倒這個(gè)問(wèn)題，所以該空格所在句子意為“長(zhǎng)頸鹿還應(yīng)該有另一個(gè)問(wèn)題”，而不是“有其他問(wèn)題”，所以D正確。排除A。

　　43. B

　　詞義辨析題。根據(jù)常識(shí)可知，長(zhǎng)頸鹿要把頭低下來(lái)喝水，所以B正確。

　　44. D

　　詞義辨析題。本句意為“長(zhǎng)頸鹿低頭喝水時(shí)，血液應(yīng)該________到大腦�！眗ush意為“沖;急流”，符合句意，所以D正確。crush意為“壓碎”，brush意為“刷”，push意為“推動(dòng)”。

　　45. C

　　詞義辨析題。根據(jù)句意可知，長(zhǎng)頸鹿頭低下的時(shí)候，血液流回到心臟比較困難，所以C正確。return作不及物動(dòng)詞時(shí)雖然也可以表示“返回”，但它本身已經(jīng)包含back的含義，所以排除。

　　46. B

　　詞義辨析題。聯(lián)系上下文可知，如果長(zhǎng)頸鹿血壓很高，那么它們會(huì)有腿部腫脹的問(wèn)題，空格所在句子就是指長(zhǎng)頸鹿對(duì)于腿部腫脹問(wèn)題的解決，所以B正確。原文第二段已經(jīng)出現(xiàn)swollen feet這一表達(dá)，根據(jù)原詞復(fù)現(xiàn)的原理也可知本題選B。

　　47. A

　　語(yǔ)法結(jié)構(gòu)題�？崭駷樗�在句子從句的引導(dǎo)詞，在從句中作賓語(yǔ)，所以A正確。

　　48. D

　　慣用搭配題。選項(xiàng)中能與out搭配的詞有figure和turn, figure out意為“計(jì)算出;解決”，不合句意，排除;turn out意為“證實(shí);發(fā)覺(jué)是”，符合句意，所以D正確。reveal意為“揭示”，indicate意為“指出”。

　　49. A

　　詞義辨析題�？崭袂暗腶nd說(shuō)明空格處的詞和skin并列，句意為“它們腿和腳上的皮膚和其他________”。tissue意為“組織”，符合句意，所以A正確。vessel意為“血管”，pore意為“小孔”，organ意為“器官”。

　　50. C

　　語(yǔ)法結(jié)構(gòu)題。空格后為兩個(gè)形容詞比較級(jí)，由此可知空格應(yīng)該是能夠修飾形容詞比較級(jí)的詞，結(jié)合句意可知，長(zhǎng)頸鹿腿和腳的皮膚和其他組織更堅(jiān)硬，所以much符合句意，C正確。

　　51. B

　　詞義辨析題。由空格前的than可知，是用長(zhǎng)頸鹿和其他動(dòng)物作比較，所以B正確。

　　52. A

　　邏輯銜接題�？崭袼�在句子意為“________長(zhǎng)頸鹿低頭喝水時(shí)，血液沖向大腦怎么辦?”根據(jù)句意可知，whenever符合句意，所以A正確。

　　53. D

　　詞義辨析題�？崭袼�在句子意為“(長(zhǎng)頸鹿的勁靜脈)能將血液從大腦________回心臟”，carry符合句意，所以D正確。

　　54. B

　　慣用搭配題。suck up意為“吸收”，suck in意為“利用;欺騙;詐取”，to和from不能和suck搭配，suck up符合句意，所以B正確。

　　55. D

　　詞義辨析題�？崭袼�在句意為“通過(guò)擠壓勁靜脈的閥門，它們能________血液流回到心臟，甚至在長(zhǎng)頸鹿喝水的時(shí)候也能�！眐eep符合句意，所以D正確。