Complete the sentences with the correct modal verb, present or past. (should, may, might, could, can't, must)

1. Mike was rude to me, and didn't even apologise. I think he ..... (say) sorry. *(it was the right thing to do)

2. I don't have my purse. I ..... (leave) it at home. *(it is possible that I left it)

3. I don't believe in what you're saying. You ..... (be) serious! *(I'm sure you are not serious)

4. Peter had an accident and he is badly injured. He (drive) so fast! *(it was wrong of him to drive so fast)