高炉富氧鼓风，有助于提高喷吹煤粉的置换比。

通过点A（0，a）的直线y=kx+a与圆（x-2）²+y²=1相交于不同的两点B、C，在线段BC上取一点P，使|BP|：|PC|=|AB|：|AC|，设点B在点C的左边，

（1）试用a和k表示P点的坐标；

（2）求k变化时P点的轨迹；

（3）证明不论a取何值时，上述轨迹恒过圆内的一定点．

汽车在平直公路上匀速行驶，下图四个图象中能正确表示汽车速度与时间关系的是（　　）

A．

B．

C．

D．

外用拔腐生肌，杀虫止痒；内服截疟的药物是( )

A．密陀僧

B．铅丹

C．轻粉

D．砒石

脑包虫病CT检查显示密度与脑脊液相似或略高，无水肿，无明显占位表现。

Under pressure from animal welfare groups, two national science teachers associations have adopted guidelines that ban classroom experiments harming animals. The National Association of Biology Teachers and the National Science Teachers Association hope to end animal abuse in elementary and secondary schools and, in turn, discourage students from mishandling animals in home experiments and science fair projects.

Animal welfare groups are apparently most concerned with high school students experimenting with animals in extracurricular projects. Barbara Orlans, President of the Scientists’ Center for Animal Welfare, said that students have been performing surgery at random, testing known poisonous substances, and running other pathology experiments on animals without even knowing normal physiology.At one science fair, a student cut off the leg and tail of a lizard to demonstrate that only the tail can regenerate, she said. In another case, a student bound sparrows, starved them and observed their behavior.

"The amount of abuse has been quite horrifying," Orlans said.Administrators of major science fairs are short-tempered over the teachers’ policy change and the impression it has created. "The teachers were sold a bill of goods by Barbara Ortans," said Thurman Grafton, who heads the rules committee for the International Science and Engineering Fair. "Backyard tabletop surgery is just nonsense. The new policies throw cold water on students’ inquisitiveness," he said.

Grafton said he wouldn’t deny that there hasn’t been animal abuse among projects at the international fair, but he added that judges reject contestants who have unnecessarily injured animals. The judges have a hard time monitoring local and regional fairs that may or may not choose to comply with the international fair’s rules that stress proper care of animals, Grafton said.

He said that several years ago, the Westinghouse Science Talent Search banned harmful experiments to animals when sponsors threatened to cancel their support after animal welfare groups lobbied for change.

The teachers adopted the new policies also to fend off proposed legislation--in states including Missouri and New York--that would restrict or prohibit experiments on animals.

Officials of the two teachers organizations say that they don’t know how many animals have been abused in the classroom. On the one hand, many biology teachers are not trained in the proper care of animals, said Wayne Moyer, executive director of the biology teachers’ association. On the other, the use of animals in experiments has dropped in recent years because of school budget cuts. The association may set up seminars to teach better animal care to its members. (414 words)

Notes: pathology 病理学。lizard 蜥蜴。tabletop 桌面。short-tempered 脾气急躁的。lobby for 游说支持。fend off 躲开。

The title which best expresses the content of the text is（）

A. Science Teachers to Ban Testing Harmful to Animals

B. Teachers’ Policy Change in Experiment on Animals

C. The New Policies of Banning Harmful Experiments to Animals

D. The Importance of Prohibiting Harmful Experiments on Animals