—Excuse me. How can I get to the library?—walk along this street you see the traffic light

问题补充：

—Excuse me. How can I get to the library?

—walk along this street you see the traffic lights. You will find it on your left.

A. before

B. after

C. until

D. when

答案：

A. before

B. after

(答案→)C. until

D. when

解析：before在……之前；after在……之后；until直到；when当……时。句意：打扰了。我怎样才能到图书馆？——沿着这条大街走，直到你看到红绿灯。你就会发现它就在你的左边。结合语境可知选C。