A. Serious
B. Intricate
C. Calm
D. Dainty
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.
