A. frivolous
B. ignorant
C. vapid
D. innocent
Flagitious : (of a person or their actions) criminal; villainous.
Frivolous : not having any serious purpose or value.
Ignorant : lacking knowledge or awareness in general; uneducated or unsophisticated.
Vapid : offering nothing that is stimulating or challenging; bland.
Innocent : not guilty of a crime or offence.
Antonym of Flagitious is Innocent