题干

下列有关哺乳动物胚胎发育和胚胎工程的叙述正确的是(  )

A:超数排卵技术要使用一定的激素如性激素、孕激素等

B:滋养层细胞发育成胎膜和胎盘是在囊胚期

C:卵裂期胚胎中细胞数目及所有细胞体积之和在不断增加

D:胚胎移植实际上是由提供胚胎的供体和孕育胚胎的受体共同完成的

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答案(点此获取答案解析)

D

同类题4

阅读下面短文,掌握其大意,然后从各题所给的四个选项(A、B、C 和 D)中,故答案选出最佳选项。

    I had worried myself sick over Simon's mother coming to see me. I was a new 1 , and I gave an honest account of the students' work. In Simon's case, the grades were awfully low. He couldn't read his own handwriting. 2 he was a bright student. He discussed adult subjects with nearly adult comprehension. His work in no way reflected his 3 .So when Simon's mother entered the room, my palms(手掌心) were sweating. I was completely 4for her kisses on both my cheeks. “I came to thank you ,” she said, surprising me beyond speech.5 me, Simon had become a different person. He talked of how he 6 me, he had begun to make friends, and for the first time in his twelve years, he had 7 spent an afternoon at a friend's house. She wanted to tell me how grateful she was for the 8 son. She kissed me again and left.

    I had nurtured(培养) in her I sat, stunned ( 惊 呆), for about half an hour , 9 what had just happened. How did I make such a life-changing difference to that boy without 10 knowing it? What I finally came to 11 was one day, several months before, when some students were 12 reports in the front of the class. Jeanne spoke13 ,and to encourage her to raise her voice, I had said, “Speak up. Simon's the expert on this. He is the 14 one you have to convince, and he can't hear you in the 15 of the room.” That was it. From that day on, Simon had sat up straighter, paid more attention, 16 more, and became happy. And it was all because he 17 to be the last kid in the last row. The boy who most needed 18was the one who took the last seat that day.

    It taught me the most 19 lesson over the years of my teaching career, and I'm thankful that it came 20 and positively. A small kindness can indeed make a difference.