Just in case, here is some additional explanations about each option in the poll:
1. I'm afraid of an immediate rejection (or that he/she will play with my feelings, not saying yes or no) and/or what comes after such rejection (awkwardness, public humiliation, taunting, harassment lawsuit, not seeing her/him anymore, lower self-esteem, feeling bad, etc.). If I knew for certain he/she would say yes, I'd go for it.
2. Initial rejection aside, even if she/he says yes it may not work out (I'll blow it somehow, I don't feel worthy of her/him, he/she will be disappointed with me or I'll be disappointed with him/her), and she/he will just reject me later (or perhaps I'll reject her/him). In short, even if I knew she/he would say yes, I still wouldn't go for it.
3. I'm afraid to approach her/him regardless of what her/his reaction will be, no matter how much I want to (not sure why). I don't know whether knowing her/his answer would help me or not.
4. All this love stuff isn't worth the effort (makes me feel uncomfortable, or weak, or ridiculous, or perverted, or scared, or I'm tired of it, etc.). I don't want things to change. I don't care what her/his answer will be.
5. None of the above. This may include some cultural or religious taboos, like the common preconception that girls "are not supposed" to take the lead, to show initiative, which is unfortunately still common.