On a warm spring morning,they arrived in London.请详细解释为什么用On
问题描述：
On a warm spring morning,they arrived in London.请详细解释为什么用On
答
某天早晨,下午都是用on
On a warm spring morning,they arrived in London.请详细解释为什么用On
某天早晨,下午都是用on