A possible way to complete this sentence is You mustn't drink alcohol when you know you have to drive.
What is the meaning of mustn't?
The word "musn't" is used for strong prohibition, for example, when an action is against the law.
How can the sentence be completed?
Based on the meaning of the word a possible sentence is:
You mustn't drink alcohol when you know you have to drive.
Learn more about modal verbs in https://brainly.com/question/18428112
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