有一个短文,最后一句话是 Weleave the zoo at half past three in the afternoon.

有一个短文,最后一句话是 Weleave the zoo at half past three in the afternoon.
We leave the zoo at___in the afternoon
A three thirty B three o'clock C three past three
a和c不都是3点半嘛,怎么选啊为什么呢