有以下程序 #include ＜iostream＞ using namespace std; static int days[]= 31,28,31,30,31,30,31,31,30,31,30,31 ; class date private: int month, day, year; public: date( int m, int d, int y ) month = m; day = d; year = y; date() void disp() cout＜＜year＜＜ - ＜＜month＜＜ - ＜＜day＜＜end1; date operator+( int day ) date dt = *this; day+= dt.day; while ( day ＞ days[dt.month - 1 ] ) day -= days[ dt.month - 1 ]; if ( ++dt.month == 13 ) dt.month = 1; dt.year++; dt.day = day; return dt; ; int main() date d1( 6, 20, 2004 ), d2; d2: d1 + 20; d2.disp(); return 0; 执行后的输出结果是
A．2004-7-10
B．2004-6-20
C．2004-7-20
D．程序编译时出错