1. It has just rained. The roads are still wet now.
2. It is late now. How long have you waited / have you been waiting?
3. Staying up / To stay up late is not good for your health.
4. Everyone in my class likes learning / to learn English.
5. It is difficult to learn Chinese well.
6. Nam has already done his homework. He is watching football on TV now.
7. This software has enabled more people to study online since its invention.
8. We have tried / have been trying to solve this / the puzzle for an hour but we haven't found the answer yet.