What makes a child speak a language has long been a puzzle to linguists. (61) speaking, there are two schools of linguists, both of whom try to explain (62) a child picks up a language so easily. The fact that a child picks a language (63) is (64) ; at one year old, a child is able to say "bye-bye"; at two, he is able to use fifty words; by three he begins to (65) tenses. The famous American linguist Noam Chomsky (66) that human beings have a sort of built-in system for language use, and that the (67) is (68) . Children are not taught language (69) they are taught arithmetic. Other linguists, (70) , hold the view that a child learns (71) of his language from the hints in the environment. (72) , theorists of both schools (73) that there is a biological basis fro language use. The (74) is which is more important, the inner ability or the environment. This is certainly a fiel
A. that
B. when
C. why
D. how
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