___________ caused the accident is still a complete mystery.
| A．What | B．That | C．How | D．Where |
Of one thing I am certain _____ hard work contributes to good results.
| A．as | B．what | C．which | D．that |
Being a good listener is a kind of quality and that’s ___ it takes to keep friendship.
| A．how | B．what | C．which | D．where |
Does it make any difference __________ he refuses or accepts the invitation?
| A．whether | B．which | C．if | D．that |
---Will you please stop that ? I’m doing my homework.
---I don’t see____it bothers you.
| A．how | B．what | C．if | D．where |
It made all the Chinese happy _______ China succeeded in sending up ShenzhouⅦ．
| A．when | B．which | C．that | D．If |