The correct answer is B. Imperative.
Explanation
The imperative is the name of the grammatical mood that is used to convey instruction, imposition, order, or requests. For example, the sentence "Talk quietly" in a library is an imperative sentence because this refers to an explicit order or rule. According to this definition when an advertisement says "Do not feed the animals" is using the imperative mode because it is making an order to the people who read this. Also, this can be identified because the first element in the sentence is an infinitive verb. So, the correct answer is A. Indicative