21.___________ control the spread of Aids, many countries have opened labs to monitor the disease.
A. Bid for B. Bid to C. In a bid for D. In a bid to
21. 答案D。考查词义辨析。bid for sth意为“投标（竞争）”；bid sb (to) do sth意为“吩咐某人做某事”；in a bid for sth / to do sth 意为“为某事而努力做”。
22. You can not imagine a child ________so cruelly.
A. to treat B. being treated C. treating D. to be treated
22. 答案B。考查非谓语动词的用法。imagine a child being treated = imagine a child’s being treated。imagine(想象) 接doing作宾语。
