20. When he entered the back yard, the farmer caught a boy _____ his apples.
A steal B to steal C stole D stealing
19. It is no use ______ about it. You can’t do anything to change it.
A. to worry B. worried C. worrying D. worries
18. I can never forget the day _______ we worked together and the day________ we spent together.
A. when, which B.which, when C. what, what D. on which, when
17. We had a picnic last term and it was a lot of fun, so let’s have______ one this month.
A. the other B. some C. another D. other
16. More and more young people are fond _______ playing tennis nowadays.
A. of B. on C. in D. with
(听力用英语周报上的题)
20、(10分)已知数列{an}满足a1＝1，an＞0，Sn是数列{an}的前n项和，对任意n∈N*，
有2Sn＝2an2+an－1
(1)计算a2，a3的值，并求数列{an}的通项公式
(2)求满足Sm≤27的m的最大值
(3)记bn＝(n∈N*)，求证：
19、(12分)如图, P为菱形ABCD所在平面外一点,M、N 分别为AD、PB 的中点，平面PAD⊥平面ABCD,PA=PD=AD=2,∠DAB=600
求证： (1)MN //平面PCD(2)AD⊥PB (3)求三棱锥D-PBC的体积
18、(6分)已知圆C：，求过点A(2，4)与圆相切的直线方程
17、(6分)在锐角△ABC中，a、b、c分别为角A、B、C所对的边，且
(Ⅰ)确定角C的大小：
(Ⅱ)若c＝,且△ABC的面积为,求a+b的值。
(n∈N*)，求证：
，求过点A(2，4)与圆相切的直线方程
,且△ABC的面积为
,求a+b的值。