Which sentence is written in the imperative mood? make sure you do your homework.
have you done your homework yet?
he did his homework after school.
i wish i had done my homework.

The sentence which is written in the imperative mood is the following one:

Make sure you do your homework.

Explanation:

At the beginning of the sentence, there is neither a subject nor an auxiliary; all  we can see is a verb: "make". That verb is in infinitive form without "to", which means it expresses an order, a command or even a recommendation (depending on context/tone), and that is what the imperative mood is all about. The sentence is an example of affirmative imperative ("Make sure"), as opposed to negative imperative (Don't make sure).

the red coloration of the lungs looks alarming and adds to the overall message that the flu is threatening apex