Even though the pure water is ____ gives sea water its main properties, the salinity of sea water affects both its weight and freezing point.
---I hear you won the prize in the English contest last week. ---That was the second time I ________ the prize.
The charity sale our school organizes every year has taught us much that we would never have________ learned in class.
---Harry, we want to know your view about the reform being carried out in our school.---OK. I ________ to that.
Tom hid himself behind the door, _________ he could hear the steps of his mother clearly.
Having a trip abroad is certainly good for the old couple, but it remains _______ whether they will enjoy it.