单项选择题
Children under 12 years of age in that country（）be under adult supervision when in a public library.
A.mustB.mayC.canD.need
单项选择题 According to a recent U.S.survey，children spend up to 25 hours a week（）TV.
单项选择题 I had to buy（）these books because I didn't know which one is the best．
单项选择题 The meal over，the managers went back to the meeting room to（）their discussion.
