定语从句典型题目Rome is the first place __you'd better visit when you travel in Italy

定语从句中规定，如果先行词，就是被修饰的名词如果是下面情形时，必用关系词 that ：
1.先行词为人和物时
I saw a boy and his dog that were walking in the park.
2.先行词有序数词或形容词最高级时
This is the most interesting book that I have ever read.
3.先行词有the only / the very / the same + 名词
He was the only person that knew how to open the safe.

而你知道 that 如果在后面定语从句中做宾语可以省略

从句缺宾语，用which 排除BC.前有the first 不用A.

D 不填