单项选择题
A.7片 B.8片 C.9片 D.10片
A.r=20.9m,D=60.95m B.r=20.9m,D=72m C.r=22.5m,D=60.95m D.r=22.5m,D=72m
A.135cm B.148.5cm C.190.9cm D.210cm