Diction is what determines a poet's A. rhyme and meter. B. words and phrases. C. structure and sound. D. subject and theme.

The correct answer is B. Diction is the term used to describe a poet's words and phrases. This is in reference to the written word however, and not to be confused with diction being used to describe the way in which words are pronounced, for example if a poet were to be reading their work out loud. So, when a poet or a writer chooses specific words to use in his or her work, that reflects their particular diction, or style of writing.