根据短文内容及首字母提示，填写所缺单词 Man has a big brain. He can think and s 1 languages. Scientists once thought that man isn't the same as animalsb 2 man can think and learn. They know now that dogs, monkeys and birds can learn, too. They are beginning to u 3 that men are different from animals because they can speak. Animals can't speak. They make much n 4 when they are afraid, or unhappy. Apes(猿) can learn some things more quickly than man. One or two of them have learned a few words. But they can not join words to make s 5 . They cannot think I 6 us because they have no language. Language is a wonderful thing. Man has been a 7 to build a modern world because he has language. Every child can speak his own language very w 8 when he is four or five, b 9 no animals learn to speak. How do children learn it? Scientists don't really know w 10 happens inside our body when we speak. They only know that man can speak because he has a brain. 1. _____ 2. _____ 3. _____ 4. _____ 5. _____ 6. _____ 7. _____ 8. _____ 9. _____ 10. _____