若有以下程序: #include usingnamespacestd; classBase {public: Base() {x=0;} intx;}; classDerivedl:virtualpublicBase {public: Derivedl() {x=10;}}; classDerived2:virtua11publicBase {public: Derived2() {x=20;}}; classDerived:publicDerivedl,protectedDerived2{};intmain() {Derivedobj; cout$amp;