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 -= tays[ dt.month - 1 ]; if ( ++dt.month == 13 dt.month = 1; dt.yeare++; dr. 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