1. 如图所示，质量为m的质点静止地放在半径为R的半球体上，质点与半球体间的动摩擦因数为，质点与球心的连线与水平地面的夹角为，则下列说法正确的是

　　　　 A、地面对半球体的摩擦力方向水平向左

　　　　 B、质点对半球体的压力大小为

　　　　 C、质点所受摩擦力大小为

　　　　 D、质点所受摩擦力大小为

49. drop　 50. bitterly　 51. succeeded　 52. to　 53. compared

[书面表达]

One possible version:

The Green School Project has become part of the environmental education in our school. However, there are still a lot of problem in the school.

　　 Very often you come across an empty classroom with the lights still on. It’s not difficult to find evidence of wasting water, a very serious problem. Additionally, students do not recycle enough, throwing away the soft drink bottles, used exercise papers and books. Worse still, many students still use the non-environmental friendly lunch boxes, causing the “white pollution”.

　　 These things should that many students lack the sense of environmental awareness. It’s important to educate students to be more environmentally friendly. At the same time, students can do small things, such as collecting used items for recycling, turning off the lights, saving water. Always remember that it’s everyone’s responsibility to protect the environment.

44.freezing　 45. gets　 46. missed　 47. said　 48. temperature　

43．C。短文的最后一句提供了答案。

[对话填空]

42．D。考古学家是根据两点判断Cave art的历史的：一些画被石笋覆盖着，而根据研究石笋已有12,800年的历史。

41．A。根据文章的第二段判断，archaeologists的意思应是考古学家。

40．C。本文主要讲述 Cave art为什么是英国最古老的艺术，文章的后半部分给出了证据。

39．A。由文章的第三段的“They came to Petaluma from Berkeley when he needed more room to paint.”。

38．B。由文章第四段的“Then she noticed homeless people.”可知。

37．A。由文章第二段的前两句可知。