跪求,现要,英语The 29th Olympic Games were held - August last year.

选A.
in+年/月,如：in 2013,in October;也可用于将来时,如:in a minute.August是八月,介词用in
on+具体的某一天（星期几/几月几日）或某一天的上中下午,如：on August 1st,on Sunday morning.
at+具体某一时刻,如at 10:00
of 我记得不能加时间