问题
you come to my birthday party tonight — I’d love to, but I______ on a patient at 6o’clock
A:it is a fun socialexperience
B:it has been developingfor over 1,000 years
C:it involves many uniqueingredients
D:will haveoperated
B:it has been developingfor over 1,000 years
C:it involves many uniqueingredients
D:will haveoperated
正确答案是：
