Trivial :

A. Serious

B. Intricate

C. Calm

D. Dainty

Answer: Option A

Solution(By Examveda Team)

Intricate : very complicated or detailed.
Calm : not showing or feeling nervousness, anger, or other strong emotions.
Dainty : delicately small and pretty.
Serious : demanding or characterized by careful consideration or application.
Trivial : of little value or importance.

Antonym of Trivial is Serious.