产品的价格背后体现的还是产品的价值量，即产品中所凝聚的人类抽象劳动的数量。商品价值取决于个别企业的劳动时间，而不是由行业平均必要劳动时间所决定。

Thanks to his ______, Martin Murray in our textbook who caused much trouble has changed a lot. [ ]

A. mother

B. father

C. pen pal

D. e-pal