Select the option that can be used as a one-word substitute for the given group of words.

Attempting to impress by affecting greater importance or merit than is actually possessed

The correct answer is Pretentious.

Explanation:
Let us analyze the meanings of the given options to find the correct one-word substitute for "Attempting to impress by affecting greater importance or merit than is actually possessed":

1. Pretentious: Refers to someone or something attempting to impress others by pretending to have greater importance, talent, culture, or merit than is actually possessed. This directly matches the given group of words.
2. Imperious: Means arrogant and domineering, assuming authority without justification.
3. Airy: Refers to something light, delicate, or displaying a casual and indifferent attitude.
4. Glorious: Means having, worthy of, or bringing great fame, honor, or magnificence.

Therefore, Pretentious is the correct one-word substitute.