________（50）A.At three he knows about 1 000 words
________（50）
A.At three he knows about 1,000 words which he can put into sentences,and at four his language differs from that of his parents in style rather than grammar.
B.What was missing was good mothering.
C.Lots of information about benefits of baby signing and best ways to go about it can be found.
D.Insensitivity of the mother to these signals dulls the interaction because the child gets discouraged and sends out only the obvious signals.
E.If these sensitive periods are neglected,the ideal time for acquiring skills passes and they might never be learned so easily again.
F.And even more incredible is the young brain’s ability to pick out an order in language from the hubbub of sound around him,to analyze,to combine and recombine the parts of a language in novel ways.
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答案：D
最后一段的主题句是：But speech has to be triggered, and this depends on interaction between the mother and the child，但是说话需要激发。这得靠母亲和孩子的互动。该空前一句从正面阐述了这一观点：母亲要善于从孩子的申申呀呀中以及依偎、抓、哭、笑中辫别出不同含义和信号，并且做出反应。选项D母亲对孩子的上述信号持冷漠态度会减弱这种相互作用，因为孩子会扫兴，而只发出明显的信号，从反面阐述了孩子和母亲之间的互相影响，是正确答案。