【单选题】---- Mary, could you come to our art club on Sunday. ---- __________.
D.
I'm sorry to hear that
【简答题】A.More than 9,000 yuan. B.Yes, it's very expensive. C.Only three computers. D.No, it's cheap.
【判断题】在光线作用下,能使电子逸出物体表面的现象称为外光电效应
【简答题】A.10,000 pounds per year. B.It's very expensive. C.Nothing, it's free. D.2 pounds per day.
【单选题】It's very expensive. It's not _________.
【判断题】古埃及人在计算等比数列求和时已经大量使用了现代等比数列求和公式。()
【判断题】在光线作用下,使物体导电能力发生变化的现象称为外光电效应
【简答题】A.It's very expensive. B.It hasn't proven to be totally effective. C.It can be damaging to some books. D.It can't be used on books published before 1850.
【简答题】数列 为等差数列, 为,其前 项和为 ,数列 为等比数列,且 ,数列 是公比为的等比数列, . (1)求 ; (2)求证 .
【单选题】在光线作用下能使( )逸出物体表面的现象称为外光电效应。