— No one can answer the question _______ we can complete the task in time, do you know? — Yes, and this is because we don’t know the way _______ the scientist used last time．

____is well-known to all, the great changes have taken place in China.

A huge amount of oil was on the road, the effects of     are not clear．

I won’t change my belief _________ success comes to those who act．

He came here in the hope　　　he could learn about the cause of the accident.