2011年北京卷高考题 几道单选题求解析!谢谢、21．Experiments of this kind in both.

2011年北京卷高考题 几道单选题求解析!谢谢、21．Experiments of this kind in both.
21．Experiments of this kind in both the U.S.and Europe well before the Second World War.
A．have conducted \x09B．have been conducted
C．had conducted \x09D．had been conducted
为什么用“had”而不用“have” 仅仅是因为是过去的事情么?
为什么有“been”?
22． Barbara Jones offers to her fans is honesty and happiness.
A．Which \x09B．What \x09C．That \x09D．Whom
为什么要用“what”,
30．Maybe if I science,and not literature then,I would be able to give you more help.
A．studied \x09B．would study\x09C．had studied \x09D．was studying
这不是主将从现么?那又是什么?为什么不选B?
34．The employment rate has continued to rise in big cities thanks to the efforts of the local governments to increase .
A．them\x09B．those \x09 C．it \x09D．that
彻底没懂、句意?指代?
以上几道高考题,3q