4. 解析:选B。根据全文内容可知，作者并不赞成克隆，对此持批评意见。

3. 解析:选B。根据文章倒数第二段“We can see that an ecosystem is composed of a lot of different kinds of life, and each life has its own function within the system. If we interfere with that, I think it could lead to our extinction”可知,B项正确。

2. 解析:选A。可从第二个原因的三个问题中总结出来。

10. 解析:选D。根据回答“没有人能在撒哈拉沙漠里生存那么久”可知，说话者并不认可Bob所说的话，因此选择D项。

9. 解析:选A。考查条件句中虚拟语气的倒装和省略。从句与过去事实相反，谓语动词要用过去完成时；提前had, if可以省略。

8. 解析:选C。burn out表示“烧坏，烧掉，烧尽”等意义，符合句意“灯灭了，他们还没有找到笔来记这个句子，所以只好记在心里”。

4. The white snow mountains contrast sharply with the brilliant blue sky on the QinghaiTibetan plateau, which is a great wonder.

3. To our great astonishment, the modern hotel was completely burnt out, only the walls left.

2. After midnight the gathering on the street still went on, and the situation gradually got out of control.

4. had never met 5. had; would lend