We’ll have to go without him （）he comes before our flight departs.
A、
if
B、
providing
C、
unless
D、
on condition that
【正确答案】：C
【题目解析】：
除非他在我们起飞前离开，否则我们只好不带他走。unless除非，符合句意。 if如果； providing以···为条件； on condition that若是。
We’ll have to go without him （）he comes before our flight departs.
We’ll have to go without him （）he comes before our flight departs.
if
providing
unless
on condition that
除非他在我们起飞前离开，否则我们只好不带他走。unless除非，符合句意。 if如果； providing以···为条件； on condition that若是。