Right answer:
c. qué hacemos
This is the more logical response to this question and translates into what do we do? Also, this is a common Spanish question when you hang out time with friends and you want to do something with them. So hacemos is the conjugation of the verb hacer that matches the first person plural (nosotros) in the simple present. Finally:
Pedro, tengo muchas ganas de ir de vacaciones, ¿qué hacemos?