(三)定语从句

　　1. The prevention and treatment of AIDS is (07.6)

　　The field in which we can cooperate

　　2. Medical researches are painfully aware that there are many problems_________ (08.12)

　　to which they still have no answers

　　强化练习

　　1. which is on the increase.

　　考点：本题考查非限制性定于从句 which 指代前句话的用法，考生不易想到。

　　2. as many famous stars who should have appeared did not come.

　　考点：在英语中表示过去应该做而实际上没有做的事，要用should + have +过去分词的句式。