the boy was walking down the street when the UFO landed改为一般疑问句,并回答 while the boy was walthe boy was walking down the street when the UFO landed改为一般疑问句,并回答while the boy was walking down the down the street ,the UFO landed（改为一般疑问）按顺序,您都把我弄晕了.

was the boy walking down the street when the UFO landed ? yes , he was
what happend while the boy was walking down the down the street ?
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was the boy walking down the street when the UFO landed ？
Yes， he is
Did the UFO land while the boy was walking down the down the street ？
Yes ， it did

Was the boy walking down the street when the UFO landed?Yes,he was.
Did the UFO land,while the boy was walking down the street?