问题补充：
This is the only one of the books on space .
A. that has been written
B. that have been written
C. which have been written
D. which has been written
答案：
(答案→)A. that has been written
B. that have been written
C. which have been written
D. which has been written
解析：这是以that引导的定语从句,修饰 the only one.
