. A look at recent trends in world fisheries reveals ________ the ocean on a global scale.

A．how we have swiftly affected

B．that how swiftly we have affected

C．how swiftly we have affected

D．however swiftly we have affected

给15g氯酸钾和二氧化锰的混合物充分加热完全反应后，剩余10.2g固体物质，则原混合物中二氧化锰的质量为[ ]

A．10.2g

B．2.75g

C．4.8g

D．10g