Answer:
The answer is D.
Step-by-step explanation:
Mood of the verb shows a manner in which a thought is expressed. There are five moods in English: indicative (stating or expressing something), interrogative (asking something), imperative (ordering something, it usually lacks subject), conditional (stating condition which needs to be met in order to fulfill something), subjunctive (expressing wishes and unrealistic conditions).
Answers A and B are indicative.
Answer C is interrogative.
Answer D is imperative (be respectful). However, this sentence also has a verb will which gives it the interrogative mood.