The days__you could travel without a passport are gone

题目

The days__you could travel without a passport are gone
这里是填at which/ in which / on which

答案

填 in which
at 后接时间点 如at 10 o'clock
on 后接具体某一天或日期 如 on Monday / on 7th April
in 后面可以接表时间范围的短语 如 in those days；
in the days to come; in the past few days