问题 选择题

下列单细胞生物中没有成形细胞核的是(  )

A.酵母菌

B.衣藻

C.大肠杆菌

D.草履虫

答案

细菌的基本结构有细胞壁、细胞膜、细胞质和DNA集中的区域,没有成形的细胞核,没有叶绿体;真菌的基本结构有细胞壁、细胞膜、细胞质、细胞核,没有叶绿体.因此细菌与真菌的根本区别在于真菌具有成形细胞核,细菌没有成形的细胞核,只有DNA集中的区域.病毒没有细胞结构,主要由内部的核酸和外部的蛋白质外壳组成,不能独立生存,只有寄生在活细胞里才能进行生命活动.酵母菌于真菌有成形的细胞核;衣藻属于藻类植物,有成形的细胞核;草履虫是动物有成形的细胞核.因此没有成形细胞核的单细胞生物是细菌,如大肠杆菌.

故选C.

单项选择题
完形填空

第二节 完形填空(共20小题,每小题1.5分,满分30分)

阅读下面短文,掌握其大意,然后从36-55各题所给的A、B、C、D四个选项,选出最佳选项,并在答题卡上将该项涂黑。

My baby Rob, the youngest of my three sons, was starting kindergarten. I had already 36 this twice before, but this time it was more difficult.

What if he was scared? What if he missed me? I decided to do the grown-up thing and not tell him how I 37. I assured him that 38 would be just fine. 

The night 39 school started, Rob and I sat down. I hugged him and asked if he had any questions about what he could expect tomorrow ... “I’m 40 excited, Mommy, but I’m a little 41 about what I should do 42 I miss you,” he said sheepishly (胆怯地).

I had just the 43 for him.

I 44 my hand and showed him a new, shiny penny. “This is a 45 magic penny. If you’re scared or if you 46 me, just put your hand in your pocket and 47 this lucky penny. 48 you hold it and 49 me, I will know and be thinking about you , too.”

It was absolutely 50. I’d be thinking about him every minute.

The next day as he 51 his schoolroom, he looked back at me. My baby looked so sure of himself. I smiled back at him and hoped that he didn’t see the 52 in my eyes.

The hours moved slowly but finally it was time to pick him 53. “I had a great day!” he 54. “There were a few times I was worried, but I held on to my lucky penny and that made me feel better.”

After about a week I found it on his dresser.  I guessed he was secure enough in his new situation that he didn’t 55 it anymore.

I, on the other hand, kept it in my pocket for a few more days.

36. A. looked into      B. gone through            C. turned into        D. brought out  

37. A. escaped            B. left               C. arrived         D. felt

38. A. everything       B. nothing            C. someone      D. something

39. A. after             B. until             C. before         D. till

40. A. really           B. seldom           C. possibly        D. hardly

41. A. worried          B. disappointed       C. pleased       D. angry 

42. A. unless                B. whenever             C. though         D. if

43. A. reply             B. answer                  C. key             D. result

44. A. closed           B. covered           C. opened         D. hid 

45. A. light            B. round             C. cheap           D. lucky

46. A. remember       B. see                  C. miss             D. refuse 

47. A. hold on to        B. take away           C. get back       D. take care of 

48. A. Some times       B. Every time        C. Any time            D. At times

49. A. turn down             B. refer to            C. think of          D. look up to

50. A. false                 B. true                C. impossible       D. uncertain 

51. A. left            B. passed            C. cleaned          D. entered

52. A. blood            B. water              C. tears            D. sweat  

53. A. out               B. up              C. in             D. away

54. A. cheered         B. signed             C. cried         D. whispered

55. A. forget            B. respect            C. help          D. need