[单选题]室外低压配电线路和设备验电宜使用（）。
A.绝缘棒
B.工频高压发生器
C.声光验电器
D.高压验电棒

It remains to be seen whether the reserves of raw materials would be sufficient to supply a world economy which would have grown by 500 per cent. South-East Asia alone would have an energy consumption five times greater than that of Western Europe in 1970. Incidentally, if the underdeveloped countries started using up petrol at the same rate as the industrialized areas, then world reserves would already be exhausted by 1985.
 All this only goes to show just how important it is to set up a plan to conserve and divide up fairly natural resources on a worldwide scale.
 This is a matter of life and death because world population is exploding at an incredible rate. By the middle of the next century population will expand every year by as much as it did in the first 1500 years after Christ. In the southern, poor, parts of the globe, the figures are enough to make your hair stand on end. Even supposing that steps are taken to stabilize world population in the n
A. natural resources might not be enough to meet the needs of world economy.
B. the supply of raw materials will increase by 500 percent.
C. the underdeveloped countries should not consume as much petrol s the industrialized areas.
D. world economy should not grow so rapidly.

How many things can you see in the night sky A lot! On a clear night you might see the Moon, some planets, and thousands of sparkling stars. You can see even more with a telescope.
But scientists believe there are some things in the sky that we will never see. We won’t see them with the biggest telescope in the world, on the clearest night of the year. That’s because they’re invisible. They’re the mysterious dead stars called black holes.
As a star’s gases burn, they give off light and heat. But when the gas runs out, the star stops burning and begins to die.
As the star cools, the outer layers of the star pull in toward the center. The star squashes (挤压) into a smaller and smaller ball. If the star was very small, the star ends up as a cold, dark ball called a black dwarf. If the star was very big, it keeps squashing inward until it’s packed together tighter than anything in the universe.
Imagine if the E
A. As its gases run out, it cools down.
B. It collides with other stars.
C. It can only live for about a million years.
D. As it gets hotter and hotter, it explodes.