题目内容：

- We'll have a hiking -Let's make it ____ half past eight ____ the morning of July 21.
A.at in B.\ on C.\ in D.about by

优质解答

选 B,make it +时间,前面不加介词了,表示约定好时间,七月二十一号上午前要用介词on,只要表示某一天的上午、下午或晚上,都要用介词on；
如：on Wednesday afternoon,on the evening of May 15th,