阅读理解
People communicate(沟通)in many different ways．The most common way is by talking with others．Besides talking，we can also use body language．When we use body language，we need to use body to show what we mean．Sign language is a kind of body language．Let’s see more about it．
Sign language is popular among dumb people who are unable to speak or don’t want to speak．If you want to communicate with a foreigner，but you can’t speak his language and he can’t speak Chinese，what can you do?Maybe you can communicate by making signs．Now let’s learn some signs Indians often use．
*When they are hungry，they move their right hands back and forth in front of their stomachs．
*When they mean“Let’s eat”．they put their right hands and move them up and down in front of their mouths．
*When they have had enough，they part their thumbs and first fingers,and move their hands from their chests to chins．
*If they have a stomachache，they put both hands on their stomachs，and move them back and forth．
为平面镜，PO为入射光线，ON为法线，入射角 
等于 
，其中符合光的反射定律的光路图是 
