单项选择题

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