四道英语题，急用。请帮帮忙。谢谢。
1 It was less than a day __________Yang Liwei , the first C hinese astronaut in space ,returned to the earth.
A. after B. before C. since D. until 答案是B.为什么不能选A 或D.?
2. Did your boss phone you againg the next day ?
No, it was ten days _____he gave me a second call.
A. before B. when C. until D. as 答案是A .为什么不能选C ,B,D?
3 Since you like the bike so much , why not buy it ?
Well , now I can't afford___bike.
A a so expensive B. that expensive a C. that an expensive D so an expensive 答案是B. 为什么?
4 By no means ______to your parents.
A is this the first time you are lying B this is the first time you have lied. C. this is the first time you tell a lie D. is this the first time you have lied 答案是D 为什么?

1.这句话的语义是：杨立伟在返回地球之前在太空中翱翔了不到一天的时间。until 的前面所接的应该是完成时态，而用在这里使这句话说得不完整，像是在介绍语境，但是却没有下文了。
2.如果是when的话，应该有个later在when前面；until同上题；as 基本表示的是两个动作一同进行，如果说一边唱歌一边跳舞这样的句子才用到它。
3.that 等于so ，然后就考虑的是so的用法了。
4.当By no means 放在句首的时候这个句子就是一个部分倒装的句型，所以D.是符合这个句型的其他的句子是不符合的。