这一题 on 后面为什么用that on that foggy a day

这一题 on 后面为什么用that on that foggy a day on that day为什么用on that day和on that day区别 Are you free on that day为什么要加on? in the day,on that day为什么一个用in一个用on拜托各位了 3Q on that day i had a f____ with my friends. I have （a）artlesson on that day. On that day,there is always a f___ moon ( ) that day A.at B.in C.on 是in that day还是on that day 究竟是that day,还是on that day?时间状语 last.next,this,that,前不用介词和定冠词,为什么有on that day