I swear I saw this in another cloze with the final α accented. What is the idea here?
Do you mean that it was γειά instead of just γεια? You will see both. Γεια is a single-syllable word, and - generally - single-syllable words are not accented. But, in older Greek they were accented, and so sometimes you do see this. Either that, or it was just a typo!