单选题 I didn't know he came back______I met him in the street.
[A] since [B] when [C] until

【正确答案】 C

【答案解析】考查连词同定搭配。not…until...是固定搭配，指“直到…才…”，符合句意逻辑。since引出从句，其前的语句应用完成时态；when引出时间状语从句，在此不符合逻辑。