There's certainly more to this poll than meets the Eye. (Haha.
![Roll Eyes (Sarcastic)](http://forum.barrowdowns.com/ubb/rolleyes.gif)
)
As Formendacil had very cleverly put it, options A, B, and D are valid, at least for me. A and B have been already explained and debated upon. In my opinion, D is not exactly nonsensical. Come to think of it, had Frodo
in any way willingly thrown the Ring, that would make him a hero far more than Gandalf or Aragorn had been, or could ever be. Frodo then would have done something Isildur had not done, Saruman would have not done, and Gandalf admitted he could not have done. The concept of the Fellowship and their division (physically) would not make sense if in the end Frodo swept all victory into his hands.
But if we're talking
direct cause, it would be A of course.