单项选择题
The first use of atomic weapons was in 1945,and their power()increased enormously ever since.
A.isB.wasC.has beenD.had been
单项选择题 Children under 12 years of age in that country()be under adult supervision when in a public library.
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.