The palace was indeed grotesque.

A. good

B. decent

C. filthy

D. congruous

Answer: Option D

Solution(By Examveda Team)

Grotesque : incongruous or inappropriate to a shocking degree.
Good : to be desired or approved of.
Decent : conforming with generally accepted standards of respectable or moral behaviour.
Filthy : disgustingly dirty.
Congruous : in agreement or harmony.

Antonym of Grotesque is Congruous