You . . . . . . . . respect your elders.

A. should

B. could

C. would

D. ought to

Answer: Option D

Solution(By Examveda Team)

Modal Verbs show us the attitude of the speaker to what is being said or done. The term "modal" means expressing mood and mood is a way to express the attitude of the speaker.
Option A expresses the mood of duty/obligation according to the sentence.