[Kahonek]

"Your submission is accepted. Your proof?"

There's a lot of anecdotal and empirical support for this statement. I meet quite a few people in my profession, and I've known only two people who are significantly attracted to both sexes. The data show that the vast majority of post-pubertal individuals across cultures are heterosexual, that there is a minority that is homosexual (1-5%, depending on how you count them), and there are very few people who have significant bisexual attraction (generally less than 1%). I think that if you truly do not feel that you have a sexual orientation (e.g. you look at very attractive men and very attractive women in the same way), that would be very rare indeed.