The correct option is A Comedy
The word 'tragedy' refers to an event causing great suffering, destruction an distress.
Option A, comedy refers to entertainment consisting of jokes and sketches, intended to make an audience laugh.
Option B, sadness refers to the condition or quality of being sad or unhappy.
Option C, victory refers to an act of defeating an enemy or opponent in a battle or competition.
Option D, seriousness refers to the quality of being stern or serious.
Thus, according to the meaning, the word 'comedy' is the antonym of the word 'tragedy'.