Answer:
Tengo que llegar para un examen
This is likely the one that completes it best. It translates into "I have to arrive for an exam" and the Spanish version would work anywhere.
However, another possible but less likely answer is Tengo que presentar un examen. In some Spanish speaking countries, this would translate into "I have to take a test". However, in some other countries it wouldn't make much sense. Thefore I would say "llegar para" best completes the sentence.