问题补充：
We didn’t know you were in trouble at that time, we would have given you a hand.
A. therefore
B. unless
C. otherwise
D. so
答案：
A. therefore
B. unless
(答案→)C. otherwise
D. so
解析：句意，我们不知道你在那个时候有困难，不然我们就会帮助你。therefore 因此 unless 除非 otherwise 否则 so 因此，根据题目意思，故选 C，
