Final answer:
The correct answer is A. will not have / is not. In the zero conditional, we use the present tense in both the if-clause and the main clause.
Step-by-step explanation:
The correct answer is A. will not have / is not.
The zero conditional is used to talk about general truths or facts. In this case, we are talking about a hypothetical situation: Sara not having a baby if she is not married.
In the zero conditional, we use the present tense in both the if-clause and the main clause. Therefore, the correct form is 'will not have' in the if-clause and 'is not' in the main clause.
Example: If it rains, the ground gets wet.