Is this sampling opportunity, self-selected or quota? (Psychology A Level)

I'm doing a create a practical question (OCR spec, 15 marker) and I'm writing about an online questionnaire, I said it was opportunity sampling even though I don't understand how it isn't self-selected because they're choosing to take part... And then I decided that I wanted an even split of male to female participation so I'd theoretically remove a number that identified as male/female but does that make it quota sampling?