第19题: [单项选择]The main purpose of the second paragraph is to ______. A. tell what is talent B. explain that intelligent children are creative. C. differentiate between creativity and intelligence. D. show that creative children are usually intelligent. 参考答案:C 答案解析:参见第2段第l句,也是这一段的主题句:For a proper understanding of children's creativity,one must distinguish creativi
第34题: [单项选择]甾体基本骨架中 A. C-5、C-6、C-7、C-8、C-9、C-10为手性C原子 B. C-5、C-7、C-9、C-11、C-13、C-15为手性C原子 C. C-5、C-8、C-10、C-12、C-14、C-16为手性C原子 D. C-5、C-8、C-9、C-10、C-13、C-14为手性C原子 E. C-5、C-9、C-12、C-14、C-15、C-19为手性C原子 参考答案:D 答案解析:甾体的基本骨架为环戊烷并多氢菲的四环结构,几乎所有天然甾体是5α系,即四个环都是反式稠合。