[简答题]Burning garbage might be one kind of energy source that we can use to help meet our energy needs. ( Passage 2)

[简答题]Burning garbage might be one kind of energy source that we can use to help meet our energy needs. (Passage 2)

[简答题]Another problem is that burning garbage can pollute the air.

[简答题]The heat that is produced by burning garbage is used to boil water. (Passage 2)

[简答题]The heat that is produced, by burning garbage is used to boil water. (Passage 2)

[简答题]Burning garbage is not a new idea. Some cities in Europe and the United States have been burning garbage for years.

[单项选择]What is the largest energy source in the US today
A. Nuclear energy.
B. Coal.
C. Oil.
D. Natural gas.

[简答题]They suggest using garbage as an energy source, and at the same time it can save the land to hold garbage.

[单项选择]Regardless of the source or kind of light, the ability of light to form an image is dependent upon just one thing--a small hole or a lens to bring the rays to a focus. The principle of image formation was discovered in early Greek Times. Later it was realized that the eye itself has a lens and that an image is, in fact, formed on the retina, the rear inside surface of the eyeball. Some man inside a cave or a darkened room noticed that light entering through a small hole in the wall formed an image on the far wall. It was observed that if you enlarge the hole, the image blurred and disappeared. On the other hand, the smaller the hole, the sharper the image-down to a certain diameter after which making the hole smaller makes the image worse again.
The function of a pinhole is to screen out all light rays except those coming in a perfectly straight line from the object, thus improving the sharpness of the image. After passing through a point the rays again spread out a little bit, an
A. keeping in touch
B. in harmony
C. small
D. different