(do sth)for the first /second ...time 这是固定短语 "第一/二...次做某事"
in +不具体的时间(年、月等)in the year1990/ in October
on+具体日子(具体某一天或说出某天的天气状况)on 12,December/ on a rainy night
at+具体钟点 at six o'clock
(do sth)for the first /second ...time 这是固定短语 "第一/二...次做某事"
in +不具体的时间(年、月等)in the year1990/ in October
on+具体日子(具体某一天或说出某天的天气状况)on 12,December/ on a rainy night
at+具体钟点 at six o'clock