China's new food law provides for a food recall system________ producers have to stop production if their food isn't up to standards.[ ]

A．where  

B．that

C．when  

D．which

胆汁可促进

A．钙、铁的吸收

B．蛋白质消化

C．糖的吸收

D．维生素A的吸收

E．维生素B₁₂的吸收