While the boy down the street, the UFO .
A. was walking; was landing
B. walked; landed
C. was walking; landed
D. walked; was landing
网友回答
A. was walking; was landing
B. walked; landed
(答案→)C. was walking; landed
D. walked; was landing
解析：考查时态：句意：当男孩正沿着街道走的时候，不明飞行物着陆了，while引导的时间状语从句经常用过去进行时态。主句用一般过去时，选C。