问题 单项选择题

.生殖细胞产生的酵素可使端粒(细胞染色体端的着丝点)重新生长,而一般细胞无法分泌这种酵素。细胞的每次分裂都使端粒受到耗损,变得愈来愈短,老化与这种耗损有关。研究人员以人体皮肤、视网膜、动脉内层的细胞做实验,这种酵素能使端粒再生出来,而不像一般细胞那样逐渐停止分裂,以致死亡。下列有关端粒、酵素的说法,不正确的一项是( )。

A.这种刺激端粒生长的酵素,是由生殖细胞分泌出来的,而一般细胞无法分泌这种酵素

B.能促使端粒再生的酵素,不会像一般细胞那样逐渐停止分裂以致死亡

C.细胞的每次分裂都耗损了端粒,这是导致人体老化的原因之一

D.通过人体细胞实验证明,生殖细胞产生的酵素具有促使端粒再生的特殊作用

答案

参考答案:B

解析:根据文意,“逐渐停止分裂而死亡”的是细胞而非酵素,酵素是由生殖细胞产生的,所以B项错误。

单项选择题 A3型题
完形填空

三、完形填空(共15小题;每小题1分,满分15分)

If you travel in some areas in India, you will be ___31_____enough to be waited on by special guide monkeys. Dressed in waistcoat, the monkeys are always ready to be at your service. Hungry, you only have to point to your own stomach and they will lead you to the __ 32 . ____33___, you put both your hands behind your head and monkeys will take you to the hotel. If you want to drink, monkeys will send you to a bar. But do not feel ___34__ when they put out their hairy hands__35____ the service is done. They’re just asking for a little money as a tip. After that, they wave their hands as if they were saying ___36___ to you .

Believe it or not, the monkeys are from the school for monkeys in India, ___37___ they were ____38____for one year to get their diplomas(学位). They’re not __39___ monkey students in the world. Some are now being trained as ___40______ in an American medical college. These monkeys ___41___ to look after patients and help them with housework.

A three- year- old monkey named Helen had learned to turn ___42___ the light, use a recorder and open doors and windows _43___ he is told to .In the tropical Malaysia where coconut trees are high up to the sky, monkeys would climb to the top and ___44____off the coconut for people. ___45__ the job is done, they would rush to their master, hoping to get some wild fruits as rewards.

31. A. calm              B. familiar      C. angry             D. lucky

32. A. shop              B. restaurant      C. hotel            D. store

33. A. Tired                   B. Thirsty        C. Angry           D. Sorry

34. A. afraid            B. surprised       C. lonely           D. concerned

35. A. before            B. while         C. after             D. till

36. A. sorry            B. hello          C. good-bye        D. thanks

37. A. when             B. which         C. where           D. since

38. A. taught            B. practised        C. trained         D. persuaded

39. A. the only           B. the same       C. different         D. living

40. A. nurses            B. workers        C. cleaners         D. waiters

41. A. are able           B. are unable      C. are about        D. have to

42. A. up and down       B. in and out      C. over            D. on and off

43. A. when             B. before         C. unless          D. till

44. A. take                B. make         C. pick            D. catch

45. A. Although          B. Since         C. Once           D. Because