Unitl tens of years ago, most zoos in such a way—animals in one area and birds in another

The professor could hardly find sufficient grounds _____his arguments in favor of the new theory.

It is said that another new car factory＿＿＿＿＿now—— Yeah.It ＿＿＿＿＿one and a half years

Is your uncle Tom a soldier— No, but he once _____ in the army for 4 years.

______you listen in class， ______mistakes you will make.