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问题 单项选择题 A1/A2型题

以下哪一项不是导致排卵前血LH/FSH峰出现的机制（）

A.雌二醇高峰对垂体的正反馈调节

B.促性腺激素释放激素的作用

C.孕酮的协调作用

D.孕酮的正反馈作用

E.下丘脑的正反馈调节作用

答案

参考答案：D

解析：大剂量雌激素对下丘脑既有正反馈作用又有负反馈作用；雌激素水平低于200pg／ml时，垂体释放FSH受到抑制，成为负反馈；雌激素水平达到200pg／ml，刺激下丘脑GnRH和垂体LH/FSH大量释放，称为正反馈；正反馈中形成的LH/FSH峰促进排卵完成。

单项选择题 案例分析题

From childhood to old age, we all use language as a means of broadening our knowledge of ourselves and the world about us. When humans first 1 , they were like newborn children, unable to use this 2 tool. Yet once language developed, the possibilities for human kind’s future 3 and cultural growth increased.

Many linguists believe that evolution is 4 for our ability to produce and use language. They 5 that our highly evolved brain provides us 6 an innate language ability not found in lower 7 . Proponents of this innateness theory say that our 8 for language is inborn, but that language itself develops gradually, 9 a function of the growth of the brain during childhood. Therefore there are critical 10 times for language development.

Current 11 of innateness theory are mixed, however, evidence supporting the existence of some innate abilities is undeniable. 12 , more and more schools are discovering that foreign languages are best taught in 13 grades. Young children often can learn several languages by being 14 to them, while adults have a much harder time learning another language once the 15 of their first language have become firmly fixed.

16 some aspects of language are undeniably innate, language does not develop automatically in a vacuum. Children who have been 17 from other human beings do not possess language. This demonstrates that 18 with other human beings is necessary for proper language development. Some linguists believe that this is even more basic to human language 19 than any innate capacities. These theorists view language as imitative, learned behavior. 20 , children learn language from their parents by imitating them. Parents gradually shape their child's language skills by positively reinforcing precise imitations and negatively reinforcing imprecise ones.

请在15处填上正确答案（）

A.regulations

B.formations

C.rules

D.constitutions
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填空题

根据交换机支持的传输速率和介质标准，以太网交换机又可分为快速以太网交换机、( )和 ( )。
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