3. Shall we use gas instead of burning coal?
I suggest using gas instead of burning coal 

4. Jane was absent from class because of her sickness.
Because Jane was sick, she was absent from class.

5. We can't afford energy-saving light bulbs because the light bulbs are too expensive.
The light bulbs are too expensive to buy, so we can't afford energy-saving light bulbs
III. Complete sentences using the words given:

1. I suggest turning off all unnecessary lights before leaving the room.
2. The city suffers from air pollution and water pollution.
3. I suggest we stop throwing trash into the water.
4. If we continue to waste water, there will be a shortage of fresh water.
5. Energy-saving bulbs should be used to save electricity.