While paying for the gas,Mary’s mother told the seller about the nice night       she had spent at the Welcome Inn.

A.in which　　　　　B.when　　　　　C.on which　　　　　D.that

While paying for the gas,Mary’s mother told the seller about the nice night      she had spent at the Welcome Inn.

1. A.
   in which
2. B.
   when
3. C.
   on which
4. D.
   that