Our sun is a star. Like all stars, it is a mass of （ 一大团）very hot gases. The sun’s energy doesn’t come from burning fuels（ 燃料 ）. The sun’s energy comes from its nuclear fusion.( 核聚变 )
How big is the sun? Its diameter, the distance across its center, is quiet huge. That’s more than 100 times the diameter of Earth. The sun’s volume is more than a million times the volume of the Earth. Another way to say this is that the sun could hold one million Earths inside it.
The sun has different layers of gases. Each layer mixes into the next, like the layers of Earth’s atmosphere.（ 大气 ） Most of the sun’s mass is in its center. It is also very hot. Almost all fusion takes place in the center.
The sun creates energy in the form of heat and light. Even though the sun is a ball of gases, it is made up of several layers. The main layers are the center. There are also other layers. The sun produces hug energy. Its energy mainly comes from its center. The sun is the source of most of the energy on Earth. Without the sun, there will be no living things on earth, including human beings.
What are the gases of the sun like?
A. Very hot
B. Very bright
C. All of the above
The sun’s energy comes from          .
A. X—rays
B. nuclear fusion
C. layers of gases
The diameter of the earth is about 6300 km. How about that of the sun?
A. About 6300km
B. About 63000km
C. About 630000km
What’s the meaning of the underlined word “ volume” according to the passage?
A. 形状                B. 面积                C. 体积
What’s the last two paragraphs about?
A. The sun has many layer.
B. Where the sun energy is from.
C. How the sun energy is made.