A/AN

Derek who is ________ university undergraduate spoke to us for ________ hour during Assembly.

1) an…a
2) a…an
3) a…a
4) an…an

The answer is 2.

Rule: Use “a” before words that start with a consonant sound and “an” before words that start with a vowel sound.

-Hour starts with a vowel sound, since it sounds like “Our.”
-University starts with a consonant sound as it sounds like “Yewniversity.”

Similarly, you say a user, an honorable person, a historic site