[اوديسا]

Do we need "double indefinite article "an, a" in the following statements or can be omitted? Make it as a rule! Besides, which one is syntactically and semantically acceptable?

Examples

Is that an expression or an idiom

Or

Is that an expression or idiom

Or

Is that expression or an idiom

Or

Without

Is that expression or idiom

[motr]Thank you & Salam in advance[/motr]