"Well done, John! Not a single mistake____  in your exam paper this time!"said the teacher.  [ ]

A. you made          

B. did you make    

C. had you made    

D. you have made

一容积为3.5×10^-4m³的容器中盛有0.30kg的水，若将一石块投入容器中后，水面恰好升到容器口，如果石块的质量为120g，求投入容器中石块的体积和密度．