According to the passage, to decide the exact amount of tax to be paid is （）.

A．Overfilling the cooker with food and water.
B．Cleaning the cooker with detergent.
C．Cooling the cooker with cold water.
D．Setting too little cooking time.

A．The gasket should be cleaned thoroughly with cold water.
B．Mild detergent and hot water can best clean the cooker.
C．Soapy water will often damage the cooker.
D．Sand can be used to clean the cooker.