问题补充:
He doesn’t have the habit of planning his travel expense, so he won’t know what to do the money runs out.
A. once
B. before
C. unless
D. though
答案:
(答案→)A. once
B. before
C. unless
D. though
解析:连词辨析。A.一旦 B.在……之前 C. 除非 D. 尽管。句意:他没有计算旅行费用的习惯,因此他不知道一旦钱用完了该怎么办。故选A。