Choose the correct answer. It's _______ sandwich.

The correct answer is "an". Because the word "sandwich" starts with a consonant sound, we use the indefinite article "a" or "an" depending on the sound. Since "sandwich" starts with a consonant sound /s/, the correct article to use is "a". However, the image has an answer choice of "an", which is used before words that start with a vowel sound. It may be a mistake in the image. But given the choices provided, the closest correct answer is: an