. It is the test system, _____ the teachers, that is to blame for the heavy burden of middle school students nowadays.
I like _____ in spring when everything turns green and active.
You can imagine what difficulty we had __________ home in the snowstorm.
We hurried to the station, ________ the train was gone.
Operation rooms should be kept free ______ bacteria of any kind.
The League Secretary and monitor ______giving a speech while the rest of the class ________ listening attentively.