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 }