1. If he isn't good at English, then he wouldn't understand what they mean.
2. If we had enough money, we would've bought those new comics.
3. ko biết huhu
4. I have never been in an earthquake before.
5. The wind have blown for three hours now.
6. The environment is affected by the pollutions in many ways.
7. If you leave the tap running while brushing your teeth, you will waste water.