几道高中英语选择题（关于复合句.正确答案已知,请给出解释）

几道高中英语选择题（关于复合句.正确答案已知,请给出解释）
1.Mother was worried because little Alice was ill,especially ____ father was away in France.
a.as b.that c.during d.if
正确答案为a,请问为什么c不对?另外可不可以填when?
2.Sarah hopes th become a friend of ____ shares her interests.
a.anyone b.whomever c.whoever d.no matter who
正确答案为c,我选了b.为什么b不对?
3.In the office I never seem to have time until after 5:30 p.m.,____ many people have gone home.
a.whose time b.that c.on which d.by which time
这题我觉得没一个选项对,但正确答案是d.请问原因?
以上3题,请高手赐教.

1.用as 或when都行,但during 是个介词,后面不能跟句子.
2.C.B不行,因为whomever同时要在句中作宾语,而____ shares her interests.从句少的是主语
3.many people have gone home 用的现在完成时,那前面用的应该是D,意思是到那个时间,许多人已经回家了.by...加时间通常句子用完成.