You can hardly imagine the difficulty the woman had________ her children.

In his lecture, the professor referred to the belief, in contrast to all other countries, ______the elderly are wise, ______is particularly dominant in the Chinese culture．

It was only a very short time _______ the young lady found her cellphone stolen as she got on the crowed bus.

It _________ there is a disaster _________ people will think much of the safety.

Not until all the fish died in the river      how specious the pollution was.