I wonder when it was __________ you came to realize __________ he said meant.

Feathers are very light,       we say "as light as a feather".

—How long do you think it will be______ man can finally solve the problem of cancer?
—Well，it depends

It sounds like something is wrong with the car’s engine. _____ , we’d better take it to the garage immediately.

_______ is expected, according to the online survey, is _______ the price of housing will not go up any more.

_________ caused the accident is still a mystery.

We had hardly arrived at the foot of the Yuntai Mountain         it began to rain heavily .

Fortunately , the adventurers brought the GPS with themselves,       they might have been lost in the desert.

It is uncertain      side effect the medicine will bring about , though about one thousand patients have taken it.