Straight. I doubt anyone is purely straight or gay, but I've considered myself 'straight' so that my attractions pretty much fit perfectly into that role. If I have any latent bisexuality, it's well-repressed.
Really? What do you base that on? I find it pretty easy to imagine that sexual preferences would be one way or the another. I have a much harder time understanding bisexuality than homosexuality, for instance.
Anyway, straight for me.
I know that in Asian cultures, they believe sexuality is kinda like a scale. Like everyone is bisexual, but it's just a matter of preference.
Rin-chan