Choose the odd one out.

The odd one out is D, Y. The other letters are all vowels. A vowel is a letter that represents a sound produced by the vocal cords with relatively open vocal tract, making the tongue relatively low and the lips relatively unrounded. The vowels in the English alphabet are a, e, i, o, and u.

Y is a semivowel, which is a consonant that is produced with a relatively open vocal tract, like a vowel. However, semivowels are not considered vowels because they are not produced with the tongue in a central position. The other semivowels in the English alphabet are w and j.