Assonance takes place when two or more words, close to one another repeat the same vowel sound, but start with different consonant sounds. Vowels are different in moth-thither, there is no assonance here.
Alliteration happens when two or more words include the same consonant sound at the<u> beginning</u> of the word. <em>Moth</em> does <u>not</u> begin with <em>th</em>, so there is no alliteration here.
Consonance is the repetition of a consonant sound and is typically used to refer to the repetition of sounds at the <u>end</u> of the word, but also refers to repeated sounds in the <em>middle</em> of a word. So the answer is consonance.
