Edison was a clever boy, and he was fourteen, he had learned advance mathematics by himse

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A. whenever
B. by the time
C. the moment
D. ever since
解析：考察时态。By the time到…时为止；根据he had learned advance mathematics by himself中的过去完成时，可知所选择的连词是与完成时连用的，结合句意可知Ｂ正确。句意：爱迪生是一个聪明的孩子。到他１４岁的时候，他已经自学了高等数学。