—Tom               in the high jump at the school sports meet last week.

—What a shame![ ]

A. do badly  

B. did well  

C. do bad  

D. did badly

有一块金属，质量为81g ，体积是30 cm³，这块金属的密度是        _____ kg/m³，若将这块金属切成两半，则其中一半的质量是       ______ kg，密度是       ______g/cm³。