Have and Of

Use have, not of, as an auxiliary verb with could, must, should, would, may, and might. Of is a preposition.

Examples:

One of the first things that you should have done was call me.

Practice:

(a) One _____ us made a mistake.

(b) It must _____ been you.

Answers to Practice Exercises

Glossary of Usage: Index of Commonly Confused Words