调查区域内的控制网点资料包括______。 A．投影面 B．地形图 C．控制点的坐标

如图所示的两平行金属扳间，存在相互垂直的匀强磁场和匀强电场，磁场的磁感应强度B₁=0.40 T，方向垂直于纸面向里，电场强度E=2.0×10⁵V/m，PQ为板间中线。紧靠平行板右侧边缘建立平面直角坐标系xOy，在第一象限内，存在着以AO为理想边界的匀强磁场B₂和B₃，B₂和B₃的磁感应强度大小相等，B₂的方向垂直于纸面向外，B₃的方向垂直于纸面向里，边界AO和y轴间的夹角为30°。一束带电荷量q=2.5×10^-8 C、质量m=4.5×10^-15 kg的带正电的微粒从P点射入平行板间，沿中线PQ做直线运动，穿出平行板区域后从y轴上坐标为(0，0.3 m)的Q点垂直于y轴射入磁场B₂区，不计微粒的重力。

（1）求微粒在乎行板间运动的速度为多大？

（2）要使进入第一象限的微粒不能通过AO边界，则匀强磁场B₂的磁感应强度大小应满足什么条件？

（3）若匀强磁场B₂和B₃的磁感应强度大小为0.60 T，求微粒从Q点进入第一象限开始，第6次通过AO边界线时的点到原点O的距离L和经过的时间t。（答案可保留根式）

The book might be my sister’s. Hemingway is________ favorite author.

A. his                    B. her                   C. my

Napoga is a 12-year-old girl in Ghana(加纳), Africa. It is hard for her family to get clean water. Every morning, she leaves home at half past five to get clean water for her family in a village far away. It takes her six hours to get enough clean water for daily cooking and drinking. She has no time to go to school or to play with her friends. Millions of people in the world are like Napoga. They can’t get enough clean water to keep healthy.
Earth Day is April 22. But on all other days, we must also remember it. The water we use is the most important natural resource on the earth.
Water covers 70% of the earth’s surface. But most of that is sea water. We can’t use it for very many things. Fresh water covers only 1% of the earth’s surface.
You probably feel lucky that your life isn’t as hard as Napoga’s. But that doesn’t mean you don’t have to worry about water. We all face serious water problems. One of them is water pollution. All kinds of things from cars, factories, farms and homes make our rivers, lakes, and oceans dirty. Polluted water is very bad for people to drink. And dirty water is bad for fish, too. Now, 34% of all kinds of fish are dying out.
How do cars and factories make our water dirty First, they pollute the air. Then, when it rains, the rain water comes down and makes our drinking water dirty. Dirty rain, called acid rain, is also bad for plants, animals and buildings.
Scientists say that in 30 years, more than half of the people in the world won’t have enough clean water. We have to learn how to save more water for ourselves and our children. Here is some advice for saving water:
· Turn off the water while you brush your teeth. You can save as much as 450 liters each month.
· Leaky taps waste a lot of water. Fix them right away!
· You can easily cut your 10-minute showers in half—and you’ll be just as clean.
· When you wash dishes, don’t let the water run.
· Only wash clothes when you have a lot to wash. If your washing machine isn’t full, you’re wasting water !

Which of the following wastes water

A．We need ten minutes if we want a clean shower.

B．We should put in enough clothes when we wash them in washing machines.

C．You can keep yourself clean by having a shower for five minutes.

D．Don’t let the water run when we brush our teeth and wash dishes.

外贸增长方式由粗放型向集约型转变，是指主要依靠提高质量、效益和优化商品结构，实现对外贸易的持续增长。

双向两车道路面中心线一般为黄色虚线。