阅读理解。 When you feel sad, tears will come down from your eyes. When you are happy, especially when you laugh hard, tears will also come down from your eyes. But tears have a more important job than showing your feelings. Tears keep your eyes clean and healthy. They wash away dirt and germs (细菌) just like bath. Your eyes also need tears to keep them wet. And eyes must be wet so that they can move smoothly. Your eyes are busy looking here and there all day long. They move quickly from one thing to another. If you didn't have tears, your eyes couldn't move, and soon you would be blind. Maybe you don't like tears, but your eyes can't do without them. 1. The story tells us ____. [     ] A. what makes people blind B. why people have tears C. why people cry when they are sad D. what tears are 2. Tears help you by ____. [     ] A. showing how you feel B. making your face clean C. washing things from your eyes D. making your eyes bright 3. If your eyes were not wet, you could not ____. [     ] A. look at things clearly B. laugh and cry C. keep clean D. show your feelings 4. When you are happy or sad, you may ____. [     ] A. look at things quickly B. wash away dirt and germs C. have tears in your eyes D. move your eyes quickly 5. The sentence 'your eyes can't do without them' means ____. [     ] A. your eyes like having baths very much B. your eyes like tears very much C. your eyes can't work without tears D. your eyes can't open without them