The letter 's' is a very common consonant in English and often appears at the end of words. Given the pattern '__a_t_', the last position could be an 's'. Additionally, 's' commonly pairs with 't' (as in 'st'), which we already know is in position 5. Words like "charts", "giants", "plants" all fit this pattern. Even if 's' isn't at the end, it could appear elsewhere in the word.