Some students often listen to music _____ classes to refresh themselves.
32. --What kind of ________ makes 3G cellphones so popular with the young? --Video communication, I think.
31. --______ one and a half days enough for the painting to be finished? --I don’t think it’s enough and only after _________ go on with it.
30. It was once called the Sea of Bamboo, but now only one fifth of the area ______ covered with bamboo, and sixty percent of other plants ______ taken the place of the bamboo.
29. When it rains, you cannot help but _______ your shoes wet.
28. The cloth _______ easily if ______ on a table.