557.In order to reduce the increasing prices of vegetables,the toll ______ if a truck carrying them passes through a toll station.
A.cancels
B.is cancelled
C.was cancelled
D.had been cancelled
558.Oh,the classroom is so dirty.It needs _____ before we begin our class.
A.cleaned
B.being cleaned
C.to clean
D.cleaning
557.答案是B;考查动词的时态。If从句用现在时，通常主句用将来时，而此句选项中没有将来时，故选B,此处表示陈述事实。
558.答案是D;need,require,want,worth,deserve后的动名词必须用主动形式，此处还可用to be cleaned来表示。
