Read these sentences and choose 'mustn’t' or 'needn’t'.

1. You _show this e-mail to anyone else. I'll trust you.

2. You_ hurry. We have plenty of time.

3. You _cook right now. We can go to a cafe.

1. You mustn't show this e-mail to anyone else. I'll trust you.

Explanation: In this sentence, the speaker is emphasizing the importance of not showing the e-mail to anyone else. The use of "mustn't" indicates a strong prohibition or obligation to not do something. The reason for this prohibition is not explicitly stated, but the speaker clearly wants the recipient to keep the e-mail confidential.

2. You needn't hurry. We have plenty of time.

Explanation: In this sentence, the speaker is reassuring the recipient that there is no need to hurry. The use of "needn't" indicates that there is no obligation or necessity to hurry. The speaker is emphasizing that there is ample time available for the task or activity in question.

3. You needn't cook right now. We can go to a cafe.

Explanation: In this sentence, the speaker is informing the recipient that there is no need to cook at the moment. The use of "needn't" indicates that there is no obligation or necessity to cook. The speaker suggests going to a cafe as an alternative option. The reason for not needing to cook is not explicitly stated, but it could be because the speaker wants to save time or prefers to eat outside.

In summary, "mustn't" is used to express a strong prohibition or obligation, while "needn't" is used to indicate that something is not necessary or required.