赞同on which 的话 那是指具体某一天而不是几天,如果是day 的话 那么答案两者都对.所以就只有选when
还有就是词句优美到问题.第一句读起来很顺.第二句的“on”“in”一起不舒服.
i will never forget the day when i stayed in your beautiful city
i will never forget the day on which i stayed in your beautiful city