I prefer to deal with big companies because their service and reputation are better than ________ of small ones.

In his lecture, the professor referred to the belief, in contrast to all other countries, _____ the elderly are wise, _____ is particularly dominant(占优势的) in the Chinese culture．

 They have done much of the work; when will ________ be finished?

In American there are more households with pets than ______ with children.

The time has come ______ we can make extensive use of nuclear energy．