Q

Why are you wearing two watches at the same time?
你为何同时戴两块表？

A

To see if the other one keeps good time.
互相监督是否走时准确。

点睛一笔

at the same time的意思是“同时”。keeps good time的意思是“（钟，表）走得准”。同时戴两块手表是为了监督是否走得准时，这实在是多此一举啊！