B．The price of a ticket for the West Lake is the highest.

C．In Disneyland, you can't see any cartoon characters.

D．The price of a ticket for the Dragon Tower is the lowest.

　　　　　　　　　　　B

When they look at the sky, people usually find the sky looks blue - not orange, red, green or yellow. Do you know why?

Unlike the moon, the earth is surrounded by an atmosphere. The atmosphere is a mixture of gasses, mostly nitrogen and oxygen. The way the sunlight travels through the atmosphere makes the sky colored.

Why blue? It doesn't look like it , but light is made up of several different colours, like you see in a rainbow. Each of these colours travels in a wave, but the wavelength (distance between the tops of each wave) varies. Red light has a long wavelength, while blue light has a much shorter wavelength. When light from the sun enters our atmosphere, the waves collide (碰撞) with gas molecules (分子). The longer wavelengths, like red and yellow, pass straight through and appear to us as "regular" sunlight. Shorter wavelengths, like blue, bump into the gas molecules and scatter in different directions. Some of it still makes it through directly, but the rest is reflected back to our eyes from all directions, so the whole sky looks blue.

The sky usually looks light blue. But it would be dark blue if you stood on top of the highest mountain, where there is less air to scatter the sunlight.

Sometimes the sky doesn't look blue. At sunrise and sunset, the light from the sun sometimes scattered in some way that you see red, orange, and other colours in the sky.

25．Why does the sky look blue?

A．The sunlight is blue itself.

B．The sunlight is made up of all the colours the same as a rainbow.

C．The blue light is scattered most among all the lights.

D．The sunlight contains only the blue light.

26．According to the passage the sky the astronaut (宇航员) sees would be ________.

A．light blue　　　 B．deep green

C．dark blue D．red or orange

27．When can you see the sky become red or orange?

A．In the morning.

B．In the sunshine.

C．When you stand on the top of a mountain.

D．When you are in space.

28．Which of the following is NOT true?

A．When you stand on the peak of the highest mountain the sky looks light blue.

B．We usually just see the blue light when the sunlight passes through the air.

C．The sky looks orange in dusk (黄昏)．

D．The red light is scattered less than the blue light.