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 }