A. indifference
B. calmness
C. despair
D. passiveness
zeal : great energy or enthusiasm in pursuit of a cause or an objective.
indifference : lack of interest, concern, or sympathy.
calmness : the state or quality of being free from agitation or strong emotion.
despair : the complete loss or absence of hope.
passiveness : accepting or submitting without objection or resistance
Antonym of zeal is indifference