Is/are with bracketed 's'

I'm composing a questionnaire and am using a question that has this kind of syntax and need to know which type is correct:

1) "State which area(s) are dirty"
2) "State which area(s) is dirty"
3) "State which area(s) is/are dirty"
4) "State which area(s) is (are) dirty"

I would like to avoid 3 and 4, as they look a bit busy, but 1 and 2 look questionable.

Thanks in advance.