Demonstrate correct use of articles and prepositions. What do you usually have for _ breakfast?

Explanation

A is used with a word that starts with a consonant sound An is used with a word that starts with a vowel sound e.g. an apple, an orange, an hour The is used before a noun to indicate that the identity of the noun is known to the reader Breakfast is such a noun that an article is almost never used before it when it is written without an adjective. For example, "I ate breakfast" not "I ate a breakfast". Thus it is the correct option