The sun is always shining. But it can only shine on one side of the earth at one time. When the sun is shining on one side of the earth, it is night on the other side. At night, you can see the stars. The stars are in the sky all day. But the light from the sun is so bright that you can’t see them. When the night comes, there is no light, and the stars are bright enough to see. The stars look very small. But some of them are even bigger than the sun. They look small because they are so far away from you. Big things look much smaller when they are far away. The sun is closer to the earth than other stars, so it looks bigger. The stars look small because ______.
选项：

A: they are far away
B: they are small
C: they have no light
D: they are in the sky