(C)21.The longest bridge linking Hongkong to Chinese mainland at Zhuhai and Macao in a giant Y- shape, is due to be completed by 2015 and to be in use for 120 years.
A. will be expected B. is expecting C. is expected D. was expected
解析：C. expect有to think or consider that something or someone is likely to come or happen “认为某人会来；认为某事会发生；预计”，不用将来时态。
(B)22. Robert is said abroad, but I don’t know in which country he is.
A. have been studying B. to have been studying C. have studied D. to have studied
解析： be said后应该接不定式形式，而且根据I don’t know in which country he is 意味着他现在仍然在国外学习，表示从过去到现在一直在做某事，要用完成进行体。所以选B，不能选D.
(D)23. Do take each subject seriously in college and even though you learn isn’t important for your life, the learning skills you acquire will be something to be cherished forever.
A. when B. where C. which D. what
解析：根据句子结构，and后是一个含有让步状语从句的一个复合句，而让步状语从句中又含有一个主语从句，what 在主语从句中做主语。故选D。
