A small car is big enough for a family of three you need more space for baggage.A. onceB.

问题补充：

A small car is big enough for a family of three you need more space for baggage.

A. once

B. because

C. if

D. unless

答案：

A. once

B. because

C. if

(答案→)D. unless

解析：题意是“如果你不需要更多的空间来放行李，那么一辆小车对一家三口来说就足够了。”unless引导条件状语从句，在此相当于if you don’t need more space for luggage.