i think the answer is "at"作者: loveblue1984 时间: 2011-1-18 21:19
at作者: asher626 时间: 2011-1-23 00:14
I strongly disagree with answering such kind of question.
obviously, he is a child, what's more, a student posting his homework.
I wonder, if you please, and think whether this sort of help would help.作者: jwjqy820 时间: 2011-1-23 00:17
on作者: 雪莲 时间: 2011-4-3 08:11
I choose B.作者: Arthur775 时间: 2011-4-3 15:07
作者: 藍藍 时间: 2011-4-3 16:03
at作者: zhuzi_xa 时间: 2011-4-3 17:12
提示: 作者被禁止或删除 内容自动屏蔽作者: 风行天下wzq 时间: 2011-4-6 08:35
on作者: maggieqiu 时间: 2011-4-6 16:14
I think to choose"on".作者: 507013899 时间: 2011-4-6 21:00
Both at(BrE) and on (NAmE)are right.作者: mypursuit 时间: 2011-4-24 22:06