---May I go and play with Tom this afternoon, mum?
---No．You can’t go out ______ your homework is being done．
A．until B．after C．before D．as
Can you ______ what I say? Do you need more explanation?
A．make sense of B．put an end to
C．attend to D．leave alone
It was at midnight ______ he got to his friend’s house．
A．when B．since C．that D．while
The global warming is more and more serious, for which human beings ______．
A．are blaming B．are to blame
C．are going to blame D．are to be blamed
--- Grace won’t like it, you know．
---______ ? I don’t care what Grace thinks．
A．So where B．So what C．So why D．So how
It is said in the book that Tomas Edison （1847-1931） _______ the world leading inventor for thirty years．
A．would be B．has been
C．was D．had been
