Reading comprehension. The sun is the largest source of light. We know that life on the earth depends on the heat of the sun. But the light of the sun is as necessary to life as its heat. Another important source of light is produced by electric sparks in tubes which has special gases. That is known as indirect light. The light we see directly from the source of light, such as sun, is known as direct light. Laser (激光) is a new kind of light source. It possesses a series of remarkable properties, which makes it a better light source in a number of cases. 1. Which is true in the following? [     ] Ａ: The light made by electric sparks in tubes with special gases is called direct light. Ｂ: Sunlight is colourless. Ｃ: Indirect light is sent from the power station and so on. Ｄ: Human beings as well as all animals depend on direct light. 2. Which is false in the following? [     ] Ａ: Sunlight is a kind of direct light. Ｂ: For man sunlight is a much more useful light than any other light. Ｃ: Electric light is more remarkable than laser in research. Ｄ: Actually moonlight comes from the sun. 3. Life on the earth can't live ____. [     ] Ａ: with sunlight Ｂ: without sunlight Ｃ: with moonlight Ｄ: without moonlight 4. Laser, as you know, ____. [     ] Ａ: has not been widely used. Ｂ: has not been researched Ｃ: is still unknown Ｄ: is less useful than any other light 5. The word 'source' means ____. [     ] Ａ: 源 Ｂ: 系 Ｃ: 种 Ｄ: 类