问题
单项选择题
致畸作用的敏感期是()。
A.着床期
B.胚泡形成期
C.器官形成期
D.胎儿期
E.新生儿期
答案
参考答案:C
解析:致畸敏感期是指对致畸作用最敏感的胚胎发育阶段,即器官形成期。在此期,胚胎细胞移动组合,形成器官原基,对致畸作用最敏感。
致畸作用的敏感期是()。
A.着床期
B.胚泡形成期
C.器官形成期
D.胎儿期
E.新生儿期
参考答案:C
解析:致畸敏感期是指对致畸作用最敏感的胚胎发育阶段,即器官形成期。在此期,胚胎细胞移动组合,形成器官原基,对致畸作用最敏感。
As a child, I was afraid of everything. At the age of 8, I even became 1 of getting Halloween candy. 2 , on October 31, my twin brother and I went out and 3 to every house in the neighborhood. Most of the houses only had a few steps to the door. It was easy. However, when we 4 one of the bigger houses with 10 tall steps 5 to the front door, which were known to have the best candy, my fear 6 me. My brother was already up the stairs, while I stood 7 at the bottom. It was 8 that I’d be able to climb all that way, for I was afraid that I might fall over in the dark and 9 my bag of candy. I might 10 my clothes on something. I wanted the candy, but there was no 11 I would go up those stairs to get it. I failed. I lost more than just candy. I lost my 12 . Fear of the unknown 13 me for a long time. After six years in nursing, I was 14 with the career I had chosen. I faced a 15 : step out into the unknown or 16 the rest of my life at the bottom of those steps, never 17 the best candy. Finally, with only $100 in my savings account, I started my own business. Whenever I would lose a client (客户), the old fears 18 . However, I’d tasted the candy, and now I don’t 19 when I face difficulties. I believe that, though 20 things can happen when we step out, worse things happen when we don’t.
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