1. Mr Quang works in a noisy environment. His hearing becomes worse.(if)
=> if Mr Quang didn't work in a noisy environment,h is hearing wouldn't become worse
2. I can't tell you unless you tell me what's wrong.(if)
=> if you told me what's wrong , I could  tell you
3. Acid rain is dangerous. Trees' leaves are damage. ( because of )
=> Trees' leaves are damage because of the dangerous acid rain
4. Fossil fuels such as coal or oil are burned. Acid gases are produced. (so)
=> Fossil fuels such as coal or oil are burned so acid gases are produced
5. Eating too much sugar can result in health problem. (lead to)
=> Eating too much sugar lead to health problem