punctuation - How do I handle articles with parenthetical statements?

If I were to use a (normal) parenthetical statement, the article would not cause problems. If I were to use a (unusual) parenthetical statement, the article seems incorrect.

How should I proceed? Is one of these options correct:

This is a (unusual) statement

This is an (unusual) statement

This is a(n unusual) statement

The last seems most appropriate to me but I suspect that is due to me and not the appropriateness of the sentence.