A.封装B.继承C.组合D.重写
A.try：语句块B.try：语句块except：语句块C.try：语句块except：语句块else：语句块D.try：语句块except：语句块else：语句块finally：语句块
A.{2，3，4}B.TrueC.NoneD.抛出异常
