I'd like to see 'none' written below 'other'. In my mind gender is a subjective, social creation so 'none' is just as valid (and silly).
Personally, I'd choose 'none' and I have a vagina. That's because having a vagina doesn't mean I know for sure what it's like to be a female. For all I know, I could think and feel exactly like a Labrador!
Given I've never been inside anyone else's head, including a labrador's, I'll never know what it's like to be anyone but me. Hence, gender doesn't exist.
Now, ask everyone what biological SEX they are and 'other' or 'none' just leaves me wondering...?!