— ______ didn’t Sally play the violin at the concert last night?

—She said that her hand hurt, but that was only an excuse. I saw her play tennis just now.

A．Why

B．Where

C．Which

D．What

设x为int型变量，请写出一个关系表达式______，用以判断x同时为3和7的倍数时，关系表达式的值为真。