11.选D
理由:D项说没有文字记录的地方就没有历史.全文最后一句否定这一说法
But where there are no written records, such spoken stories are often very helpful
12 选D
理由:第2段 But we know almost nothing about the people who lived even 200 years ago in central Africa, because they had not learned to write.
13.选D
理由:最后一段
14.选B
理由：remembered history是口传唱歌跳舞的形式记录的历史It is not so exact or so valuable to us as written history is,
在有文字记录的时候没有意义．
15.选 A