One who is not easily pleased by anything

A. Maiden

B. Mediaeval

C. Precarious

D. Fastidious

Answer: Option D

Solution(By Examveda Team)

One word substitution is Fastidious.

Maiden: an unmarried girl or young woman.
Mediaeval: relating to the Middle Ages.
Precarious: not securely held or in position; dangerously likely to fall or collapse.
Fastidious: very attentive to and concerned about accuracy and detail.