The correct answer is: 42531.
The word “now” is an adverb that indicates the present time. The word “must” is a modal verb that indicates necessity. The word “leave” is a verb that means to go away from a place. The word “you” is a pronoun that refers to the second person. The word “not” is a negative word.
The sentence “You must not leave now” means that you are not allowed to leave at the present time. This could be because it is not safe to leave, or because you have something else that you need to do.
The other options are incorrect because they do not make sense in the context of the sentence. Option A, 25134, is not a grammatically correct sentence. Option B, 32154, is a grammatically correct sentence, but it does not mean the same thing as the original sentence. Option C, 15423, is a grammatically correct sentence, but it does not make sense in the context of the sentence. Option D, 42531, is the only option that is both grammatically correct and makes sense in the context of the sentence.