环境保护要坚持以综合治理为主，集中力量先行解决危害群众健康的突出问题。[ ]

木材表面发生石墨化是由（）形成的。

A、灼热体灼烧

B、辐射着火

C、低温燃烧

D、电弧灼烧

2007年10月31日，我国将“嫦娥一号”卫星送入太空，经过3次近月制动，卫星于11月7日顺利进入环月圆轨道。在不久的将来，我国宇航员将登上月球，届时“嫦娥号”飞船将进入绕月飞行的圆形轨道a，如图，当飞船运动至A点时启动登月舱进入椭圆轨道b，到B点实现着陆，（椭圆轨道的一个焦点在月球中心，A、B分别为与轨道a和月球表面相切点）。已知月球质量为M，半径为R，轨道a半径为r，万有引力常量为G。试求：

（1）飞船绕月飞行的周期T_a；

（2）登月舱由轨道a进入轨道b时，在A点应启动发动机，向前喷气还是向后喷气？从A点到B点的时间是多少？

已知在反应3A+2B==2C+D中，反应物A、B的质量比为3∶4。当反应生成C和D的质量共140g时，B消耗的质量为_______g。

People living more than three thousand meters above sea level find it difficult to raise vegetables all year long. People living in the highlands of Peru and Bolivia, for example, cannot grow vegetables outdoors during the months of May through September. It is very cold in the highlands at that time of year. If traditional farming methods are used, vegetables will not survive.

However, there is another way to grow vegetables throughout the year in cold areas. It is a method of gardening developed by a private agency called World Neighbors. The method uses “hot houses” built below ground. A hot house is a building covered with plastic or glass in which vegetables or flowers are grown. The traditional hot house is built above ground.

The air temperature is cold in the highlands of Peru and Bolivia during the winter. But, the winter sun is hot. So, World Neighbors advises farmers there to build hot houses below ground. The design is simple. The material does not cost much. Here is how World Neighbors says to build it: Dig a hole two and one-half meters wide and six meters long. Make it about two meters deep. Build wall with a door in one end of the hole. Dig steps from the ground down to the door.

Now, build a wall along the top edge of the hole. Make it about one-half meters tall. Earth bricks work fine. Build two shorter walls on the ends. These will be uneven; one side will be as high as the existing wall. The other side will be at ground level. Leave a small opening in each of these sloping walls. This prevents the hot house from becoming too hot. Now, make the roof. Build a wood frame. Cover it with clear plastic. Connect it to the brick walls.

The underground hot house we have described is large enough for two raised vegetable beds. Each is one meter wide and six meters long. Each is seeded and watered just as if it were in a garden above ground.

The dirt walls protect the growing plants from the cold. The clear plastic roof permits the sun’s heat to enter. At night, the roof should be covered with straw. This helps prevent cold air from entering. An under ground hot house this size will provide enough vegetables for one family. Groups needing more vegetables can make it bigger.

66. If you lived in Peru, you _______.

A. should raise the special kinds of vegetables that can endure cold

B. could not plant at all

C. had to work out some new unusual plans

D. would not have many vegetables to eat

67. To our surprise, the “hot houses” invented by World Neighbors are _______.

A. covered with a transparent plastic ceiling

B. built under ground

C. quite small

D. hotter than traditional ones

68. The hot house can be kept warm by using _______.

A. a big oven  B. an electricity heater

C. the heat of the earth’s interior   D. the sun shine

69. The measure to prevent the hot house from becoming too hot is to _______.

A. make the roof sloped B. dig holes on the walls

C. make the wall not vertical D. make the walls shorter than the ground level

70. According to the passage, the method suggested by World Neighbors is _______.

A. new and difficult      B. uneasy to explain

C. at trial step D. simple and practical

钙离子与EDTA形成络合物的配合比是（）。

A.1：3

B.1：1

C.1：2

D.1：4