Our rivers are running dry or being polluted. If we go on ignoring this, the consequences (后果) will not be hard to predict.改写为：If we go on ignoring our rivers are running dry or being polluted, the consequences will not be hard to predict.

( ) of the rivers here have been polluted. ( ) of the rivers here have been polluted.

Many lakes and rivers ________ by industrial waste. A: A have polluted B: B have been polluted C: C had been polluted D: D has been polluted

‍If we had taken such effective measures much earlier, the river _____ so seriously now.‎ A: is not polluted B: would not be polluted C: had not been polluted D: would not have been polluted

Some places, ______ their severe weather condition, are hardly polluted.

The river ______ very clean ten years ago, but now it is polluted.

Generally, air will be polluted _______ there are factories.

Rives _ used to be polluted by industrial chemical waste.

______ there are a large number of chemical factories, the air is likely to be polluted. A: That B: Where C: Once D: As

Breathing such polluted air is the _______ of smoking ten cigarettes a day.