单项选择题
A.MBD=Ph/4,MAC=Ph/4 B.MBD=-Ph/4,MAC=-Ph/2 C.MBD=Ph/2.MAC=Ph/4 D.MBD=Ph/2,MAC=Ph/2
A.I2=I3 B.I2=4I3 C.I2=2I3 D.I3=4I2