______ the prices of color TV sets down by 50%, the company had a very hard time.

A．As

B．With

C．Because of

D．For

销售发票是应收账款系统最重要的原始数据之一，系统必须具有进行销售发票的新增、修改、删除、查询、打印、审核和记账等功能。 ( )