We'll have to go without him unless he ______ before our train d

We'll have to go without him unless he ______ before our train departs.
A、come
B、comes
C、has come
D、will come
【正确答案】：B
【题目解析】：译文：除非他能在我们的火车启动之前赶到，否则我们只好不等他自己走了。此句为unless引导的条件状语从句。在条件状语从句中，从句常常用一般现在时表将来。答案为B。