they found it was very hot in day ,and very cold at night there.是第一个填the.第二个不填吗为什么?
问题描述：
they found it was very hot in day ,and very cold at night there.
是第一个填the.第二个不填吗
为什么?
答
in the day在白天
at night在晚上
都是泛指,固定用法