Question

_______ the boy was walking down the street, the UFO landed.

A．While

B．After

C．Before

D．until

Answer 1

A

試題分析：句意：當(dāng)這位男孩在街道上散步時(shí)，UFO著陸。While當(dāng)……的時(shí)候；after在···……之后；before在……之前；until直到。所以選A。