请问选哪个?为什么?What did you think of me when you saw me ___ the f

正确答案：C,for.
句子意思：
当你第一次看见我的时候,你认为我怎么样?
知识链接：
要表达【某人第一次做某事】,在英语中经常可以表达为：
sb 【do/did sth for the first time】
sb【 first do/did sth 】 这两个是【 for the first time、first做时间状语】
或
the first time sb do/did sth【the first time 引导时间状语从句,不用介词.】
这里考察 固定短语,因此,只能选C.
结合你所给句子,这三种表达分别可以变为：
What did you think of me when you saw me for the first time?
=What did you think of me when you first saw me
=What did you think of me the first time you saw me
祝你开心如意!