【单选题】

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 first (31) they were like newborn children, unable to use this (32) tool. Yet once language developed, the possibilities for human kinds’ future (33) and culture growth increaseD、

Many linguists believe that evolution is (34) for our ability to produce and use language. They (35) that our highly evolved brain provides us (36) innate language ability not found in lower (37) . Proponents of this innateness theory say that our (38) for language is inborn, but that language itself develops gradually, (39) a function of the growth of the brain during childhooD、Therefore there are critical (40) times for language development.
Current (41) of innateness theory are mixed, however, evidence supporting the existence of some innate abilities is undeniable. (42) more and more schools are discovering that foreign languages are best taught in (43) grades. Young children often can learn several languages by being (44) to them, while adults have a much harder time learning another language once the (45) of their first language have been firmly fixeD、
(46) some aspects of language are undeniably innate, language does not develop automatically in a vacuum.Children who have been (47) from other human beings de not possess language. This demonstrates that (48) with other human beings unnecessary for proper language developments. Some linguists believe that this is even more basic to human language (49) than any innate capacities. These theories view language as imitative, learned behavior. (50) , 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.
Above all
B．In other words
C．After all
D．As a result