Because of the economy drive, they very unwillingly surrendered some superfluous posts.

important
relevant
significant
essential

The correct answer is A. important.

Superfluous means “more than is needed or wanted.” In the context of the sentence, the people are very unwillingly surrendering some posts that are not essential. Therefore, the posts must be important.

B. relevant is incorrect because the posts are not relevant to the economy drive.
C. significant is incorrect because the posts are not significant enough to warrant keeping them.
D. essential is incorrect because the posts are not essential to the economy drive.