II. Complete the sentences. (must, mustn't, have to, don't have to, doesn't have to). 1. They_
eat too much cake.
2. We_
leave now or we'll miss the plane.
3. Tom_
_take a bus because his dad drives him to school every morning.
4. It's getting late. I think l_
go now.
5. Doctors sometimes_
work at the weekends.
6. You_
be on time for the exam.

1. They mustn't eat too much cake.
Explanation: The speaker is giving a prohibition or a strong advice to not eat too much cake. The use of "mustn't" indicates that it is necessary to avoid eating too much cake.

2. We have to leave now or we'll miss the plane.
Explanation: The speaker is stating an obligation or necessity to leave at that moment in order to avoid missing the plane. The use of "have to" suggests that there is a requirement to leave immediately.

3. Tom doesn't have to take a bus because his dad drives him to school every morning.
Explanation: The speaker is explaining that it is not necessary for Tom to take a bus because his dad already provides transportation for him to school every morning. The use of "doesn't have to" indicates the absence of obligation.

4. It's getting late. I think I must go now.
Explanation: The speaker is expressing the necessity or obligation to leave because it is becoming late. The use of "must" suggests that the speaker has no choice but to go now.

5. Doctors sometimes have to work at the weekends.
Explanation: The speaker is stating that there are occasions when doctors are required to work during the weekends. The use of "have to" indicates the obligation or necessity of working on those particular days.

6. You must be on time for the exam.
Explanation: The speaker is giving a strong advice or requirement to be punctual for the exam. The use of "must" indicates that it is highly necessary to arrive on time.

I hope this explanation helps you understand the use of "must," "mustn't," "have to," "don't have to," and "doesn't have to" in completing the sentences.