A. In aerobic bioremediation, oxygen is the electron acceptor, and is required for the oxidation-reduction reactions that transform the organic contaminants (petroleum hydrocarbons) to carbon dioxide and water.

• 答：在有氧生物降解过程中，氧是电子受体。原先的有机污染物（石油烃类）被转化为二氧化碳和水。