It was not he took off his dark glasses I realized he was a famous singer.A. when; thatB.

问题补充：

It was not he took off his dark glasses I realized he was a famous singer.

A. when; that

B. until; that

C. until; when

D. when; then

答案：

A. when; that

(答案→)B. until; that

C. until; when

D. when; then

解析：句意：正是直到他摘下他的墨镜我才意识到他是一个著名的歌星。not......until......直到......才.......; . 强调句的结构：It was +被强调的内容+that+剩余内容；第一空not until he took off his dark glasses是被强调的内容，第二空用that来引导剩余内容。故选B。