I'm choosing 'a' because it's one of the most common vowels in English. Since we already know there's an 'e' in the 5th position, it's likely that another vowel appears elsewhere in the word. The word has 6 letters total, and common word patterns often include an 'a' in the first or second position. Additionally, many 6-letter words with 'e' as the fifth letter might end with 'r' forming an '-er' ending, and often have an 'a' earlier in the word.