单项选择题
A.productive B.communicative C.aggressive D.protective
We watched the plane（）behind the clouds.A.disappearingB...
单项选择题We watched the plane（）behind the clouds.
A.disappearing B.disappeared C.diving D.dived
Pipes made of plastic are now widely used in building ...
单项选择题Pipes made of plastic are now widely used in building as they are light and do not become （）in water.
A.ripe B.instant C.rotten D.mature
They were under the（）that the company was doing well, ...
单项选择题They were under the（）that the company was doing well, but in fact it was in serious trouble.
A.conclusion B.expression C.enjoyment D.illusion
