题目内容：
根据下列材料请回答题：From childhood to old age, we all use language as a means of broadening our knowledge of ourselves and the world about us. When humans first1 , they were like newborn children, unable to use this 2tool. Yet once language developed, the possibilities for humankind' s future 3and cultural growth increased. Many linguists believe that evolution is4for our ability to produce and use language. They 5thatour highly evolved brain provides us 6an innate language ability not found in lower 7 . Proponents of this innateness theory say that our 8 for language is inborn, but that language itself develops gradually,9 a function of the growth of the brain during childhood. Therefore, there are critical10 times for language development.Current11 of the innateness theory are mixed; however, evidence supporting the existence of some innate abilities is undeniable. 12 , more and more schools are discovering that foreign languages are best taught in13 grades. Young children often can learn several languages by being 14to them, while adults have a much harder time learning another language once the 15of their first language have become firmly fixed.
16 some aspects of language are undeniably innate, language does not develop automatically in a vacuum. Children who have been17 from other human beings do not possess language. This demonstrates that 18with other human beings is necessary for proper language development. Some linguists believe that this is even more basic to human language19 than any innate capacities. These theorists view language as imitative, learned behavior. 20, children learn language from their parents by imitating them. Parents gradually shape their child' s language skills by positively reinforcing precise imitations and negatively reinforcing imprecise ones. A．generated
B．evolved
C．born
D．originated
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