It was he took off his dark glasses I realized he was a famous singer.
A. until，that
B. not until，that
C. not until，when
D. when，then
网友回答
A. until，that
(答案→)B. not until，that
C. not until，when
D. when，then
解析：：考查强调句型。强调句型：it is/was本强调成分that/who其它成分；本题强调时间状语not until he took off his dark glasses;句意：直到他摘掉眼镜，我才意识到他是一个著名的歌手。故B正确。