Is your sister _____ kids? [ ]
A. good for
B. good at
C. good on
D. good with
答案:D
体积为8的正方体,其全面积是球表面积的两倍,则球的体积是
下列物质含有极性共价键的离子化合物是
A.H2S
B.Na2O2
C.NH4Cl
D.CaBr2