1.   As a presidential candidate, Bush contended that the air and water in Texas had in fact become cleaner during his tenure.

2.   Buses have also become much cleaner.

3.   Experts say the reason is they are not as flexible as gasoline cars, and policy-makers have become reconciled to gasoline as engines have become cleaner and oil cheaper.

4.   He predicted the disagreement with the city would be worked out quickly and the subways would soon become cleaner as thousands of welfare recipients began working for their benefits.

5.   In recent years, as parks and marshes have become cleaner, the graceful birds have become a fairly common sight throughout the metropolitan area during summer months.

6.   Some large industries have become cleaner or moved away from Mexico City.

7.   The appearance of the salmon, a fish that is choosy about water quality, seemed proof that the river was at last becoming cleaner.

8.   The two diseases only returned when the air became cleaner.

9.   When the Clean Air Act was written, many people assumed that emissions from power plants would become cleaner as new plants replaced old ones.

10.   Yet in recent years it has become cleaner and small stocks of brave fish still make their way again upstream.