Question

Next week on Thursday my friend Marcus.....a party to celebrrate his twenty - first birthday. (have) 

 

Answer 1

is going to have 

Answer 2

1) Next week on Thursday my friend Marcus will have a party to celebrrate his twenty - first birthday. - Future Simple
2) Next week on Thursday my friend Marcus is going to have a party to celebrrate his twenty - first birthday.  - to be going to - собираться что-то делать
3) Next week on Thursday my friend Marcus is having a party to celebrrate his twenty - first birthday - Present Continuous в значении Future Simple (давно запланированное действие)

На следующей неделе в четверг мой друг Маркус будет праздновать свой двадцать первый день рождения.