【答案】I didn't know he came back _______ I met him in the street.

I didn't know he came back _______ I met him in the street.

A. while B. when C. after D. until

【答案】

D

【解析】

句意：直到我在街上遇到他我才知道他回来了。句型：not……until直到……才。while当……时；when当……时；after在……后。根据语境：直到我在街上遇到他我才知道他回来了。故答案为D。