问题
选择题
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
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。