Answer:
c) the condition subsequent has occurred;
Explanation:
Since in the question it is given that the John and his wife Martha get a divorce and according to the divorce settlement contract she agrees to pay the alimony to John for $5,000 per month for his lifetime or until that time when he should remarry
If John remarries after three years, so the alimony benefits is ceased because the subsequent condition has occurred due to which he will not get the amount further in the future