She was a good student when she was____

问题描述:

She was a good student when she was____
A in the school B at the school
C at school D in school

C
表示在读书的时候
A表示在学校里,但是任何人都可以在学校里,包括扫地的阿姨.但是不表示读书
C是固定用法,在读书期间