MẤY BÀI NÂNG CAO ĐÂY, THA HỒ MÀ LÀM!!
1. It was a mistake not to bring your umbrella.(should)
2. I can imagine hơ worried Tom's father was.(must)
3. It is possible that one of the men died on the mountain.(may)
4. It was not necessary for you to do all this work.(needn't)
5. It was a mistake...