用括号中所给词的适当形式填空。
That kind of bags is ________ (use), we can use it over and over again.
The river outside the city _______ (pollute) by the factory nearby in the past few years.
Those animals are ________ (give) food three times a day.
The scientists _________ (come) up with some good ideas to solve the serious problem already.
The soldiers are _______ (try) to save more people.