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

(聽(tīng)力用英語(yǔ)周報(bào)上的題)

20、(10分)已知數(shù)列{a_n}滿足a₁＝1，a_n＞0，S_n是數(shù)列{a_n}的前n項(xiàng)和，對(duì)任意n∈N*，

　有2S_n＝2a_n²+a_n－1

　(1)計(jì)算a₂，a₃的值，并求數(shù)列{a_n}的通項(xiàng)公式　

　(2)求滿足S_m≤27的m的最大值　　　

(3)記b_n＝(n∈N*)，求證：

19、(12分)如圖,　 P為菱形ABCD所在平面外一點(diǎn),M、N 分別為AD、PB 的中點(diǎn)，平面PAD⊥平面ABCD,PA=PD=AD=2,∠DAB=60⁰

求證： (1)MN //平面PCD(2)AD⊥PB　 (3)求三棱錐D-PBC的體積

18、(6分)已知圓C：，求過(guò)點(diǎn)A(2，4)與圓相切的直線方程

17、(6分)在銳角△ABC中，a、b、c分別為角A、B、C所對(duì)的邊，且

(Ⅰ)確定角C的大�。骸� 　

(Ⅱ)若c＝,且△ABC的面積為,求a+b的值。