Correct option is C
(a) War: This is related but is not an opposite of conflict.
(b) Anger: This can be related to conflict but is not an opposite.
(c) Harmony: This represents a state of peace and is the opposite of conflict.
(d) Competition: This is related but not an opposite of conflict.
Conclusion: The term that is to conflict as sorrow is to happiness (an opposite) is (c) Harmony.
So, the answer is: (c) Harmony.