1．She’ll be back __________a week．
A．after B．in C．from D．at
2．We didn't know the good news _________he told us．
A．after B．or C．because D．until
3．There will be _____ pollution this year than last year.
A．fewer B．much C．less D．many
4．While the boy ______ down the street, the UFO _____ .
A．was walking; was landing B． walked; landed
C．was walking; landed D． walked; was landing
