1. Now the air isn't clean in this city. There is air _______ here and there.
2. Your hands look so ________ (脏). Go and wash them.
3. He doesn't study hard, so he often ________ (doesn't pass) in the exam.
4. Please set us a good ________. (榜样)
5. Don't _______ (make fun of) at the weak. We should go to help them.