单选题 Scientists do not know ________.A. how children learn their own languagesB. when children begin to learn their own languagesC. why children learn their own languages
【正确答案】 A
【答案解析】[解析] 本题属于推断题。根据文章最后四句话可以推断，A所表述的是正确的。故本题答案为A。