1. If Mr. Quang works in a noisy environment, his hearing will become worse.
2. If you don't tell me what's wrong, I can't tell you.
3. Because of the dangerous acid rain, trees' leaves are damaged.
4. Fossil fuels such as coal or oil are burned, so acid gases are produced.
5. Eating too much sugar leads to health problems.
6. After David had gone home, we arrived.
7. Before had lunch, we took a look around the shops.
8. When we got out of the office, the light had gone out.
