Final answer:
Diaeresis is the division of a word into syllables to ensure vowels are pronounced separately. It's an orthographic and pronunciation concept, different from elision or caesura in poetry (option A).
Step-by-step explanation:
The term diaeresis refers to the division of a word into syllables when pronunciation requires that two adjacent vowels are pronounced separately rather than together. An example of diaeresis can be seen in the word 'coöperate,' where the two 'o's are pronounced as separate syllables, ensuring clarity in speech. Diaeresis is not to be confused with elision, which is the omission of a syllable or a vowel at the end of a word to fit a poetic rhythm, or with a caesura, which is a pause in a line of poetry.
Hence, the answer is option A.