I tend towards B... I'd of course we wary to be sure she's not experimenting with me. And if she is, she'd at least need to tell me. It would change the dimension of our relationship, though I would not necassarrily walk away. It would than depend on her attitude and if she'd gradually become very serious about us. Otherwise, friend zone is okay... but no messing around with someone who's not serous about us :o
It depends on the circumstances, I wouldn't want to be used so she could test the waters so to speak so their would have to be some reason for the sudden shift, beyond that I don't think I would mind that much as long as she didn't expect me to act differently.
That's a lot of responsibility: I'd be responsible for the first hetero experience, thus I would be representing the whole man gender. She would encapsulate her idea of a man based on everything I'd do. I would feel that she'd be comparing me at all times and thinking how it would be like if I was a woman. And I'd feel threatened, as it it wasn't enough to have half of the planet's population as a competition, now I had the other half aswell.
My biggest worry would be that I would be afraid of annoying her by asking her about details of lesbianism. i would find it amazingly hot, and I worry she would find my interest (not in her ex, but in her bisexuality) trying.
I think if they had only ever been with the same sex before I would be a little worried that I was like their straight experiment and question if it was a relationship that I should really get invested in. It depends on a lot of other things though. If they identified as completely gay before me then it would validate my concerns but if they had always felt they were bi and just never made it around to the opposite sex yet I wouldn't feel as threatened by it. I think it's probably some lack of self confidence on my part but even at that it would probably keep me a little more reserved right at the start of the relationship. Obviously at a point if the relationship is lasting it won't seem as odd and the whole thing will fade out of my mind - the feeling that they might leave for lack of interest, not the knowledge that they had never been with the opposite sex before. I kind of feel like all of the poll options at once, really.
I wouldn't be able to handle it. It would make me think that he needs more sexually than I can give. I would expect him to always want a man over me. I can't compete with another man for my man's attention. So, nope.