Question

【题目】_______ the boy was walking down the street, the UFO landed.
A.While
B.After
C.Before
D.until

Answer 1

【答案】A
【解析】句意：当这位男孩在街道上散步时，UFO着陆。While当……的时候；after在···……之后；before在……之前；until直到。所以答案是A。