The correct answer is A. David told Anna that Mona will leave for her native place tomorrow.
Option B is incorrect because it uses the past tense, “left.” This is not consistent with the fact that David is speaking about something that will happen in the future.
Option C is incorrect because it uses the infinitive form, “to be leaving.” This is not consistent with the fact that David is speaking about something that is certain to happen.
Option D is incorrect because it uses the past tense, “would leave.” This is not consistent with the fact that David is speaking about something that will happen in the future.
In addition to being the correct answer, option A is also the most concise and direct way of stating what David said.