We go and do some shopping （ ） Sunday morni

此处填on.in 用在 in the morning 、in the afternoon 、in the evening .而涉及到具体某一天的某个时辰要用on.此外,in还能用在：① in+年份 如：in 2013 ②in+季节 如：in autumn ③in+月份 如：in October ④ 就是in the morning等 而on用在：① on+具体某天 如：on sunday、on sunday morning ②on+日期 如on October 19th ③ on+节日 如 on New Year's Day