问题补充：
Is this school they visited the other day?
A. that
B. which
C. where
D. the one
答案：
A. that
B. which
C. where
(答案→)D. the one
解析：这句话变成陈述语序：This school is (the one ) you visited the other day. the one是补出来的先行词，不然主句里缺表语。在the one的后边紧跟的是一个that引导的定语从句， 从句中省略了that,因为它在句中做visit的宾语。 直接用that代替，也不是宾语从句，是表语从句，而that引导名词性从句（包括表语从句宾语从句等）在从句中是无成分无意义的，而从句中visit后边缺宾语。
