The current pattern is _IRA__E, and a word that fits this pattern well is 'giraffe' – an animal whose letters match the pattern perfectly: G I R A F F E. The letters we have already guessed (a, e, i, r) appear in 'giraffe', and the remaining missing letters would be G and F. Since F appears twice, guessing it could reveal more of the word. Therefore, I'll guess the letter F.