下面程序的运行结果是 #include<iostream.h> class base{ protected: int a; public: base( ) {cout < < "0";} }; class base l: virtual base{ public: base l ( ) {cout < <"1";} }; class base 2: virtual base{ public: base2 ( ) {cout < <"2";} }; class derived: public base 1, public base2{ public: derived( ) {cout < < "3";} }; void main( ) { derive obj; cout < < endl;} A) 0123 B) 3120 C) 0312 D) 3012