The boys are good at running.They will take part in the____race.

问题描述:

The boys are good at running.They will take part in the____race.
A.boy's 400-meter B.boys' 400-meters C.boy's 400-meters D.boy's 400-meter

ad 答案一样啊,打错了吧?
应该选ad 不过是boys' 400-meter