I don't believe we've met before, I must say you do look familiar.
A. therefore
B. although
C. since
D. for
网友回答
A. therefore
(答案→)B. although
C. since
D. for
解析:考查引导词,therefore表示因此;although 表示尽管…但是…;since表示自从…;for表示为了…,句子意思“尽管我不相信我们以前见过面,但是我必须说你看上去很熟悉”,句子I don't believe we've met before是个宾语从句,省略了引导词that,look系动词,后跟形容词