Man has a big brain. He can think, learn and speak. Scientists once thought that men are different from animals ___(1)___ they can think and learn. They know now that dogs, monkeys, birds can learn, too. They are beginning to understand that men are different from animals because they can speak. Animals can't speak. They make noises when they are afraid, or unhappy. Apes can understand some things ___(2)___ than man. One or two of them have learned ___(3)___ words. But they cannot join words to make sentences. They cannot think ___(4)___ us because they have ___(5)___ language. Language is a wonderful thing. Man has ___(6)___ build a modern world because he has language. ___(7)___ child can speak his own language very well when he is four or five, ___(8)___ no animals learn to speak. ___(9)___ do children learn it? Scientists don't really know. ___(10)___ happens inside our body when we speak? They don’t know. They only know that man can speak because he has a brain.