The result of flipping an evenly weighted, or "fair, " coin, a process commonly thought to be random, is, in fact, well determined by the impulse given the coin and by the height above the floor from which the coin starts. Yet it is difficult to predict the result of a fair coin flip. Which of the following, if true, contributes most to an explanation of why the outcome of a coin flip is difficult to predict even though it is well determined? ['Coin flipping has been used as a prime example of a random process for decades.', 'That the results of coin flipping are well determined runs counter to the randomness that physicists have been finding in more and more processes once thought to be determined.', 'An accurate prediction of the result of a coin flip requires extraordinarily precise estimation of height and impulse.', 'If the impulses of coin flippings remain perfectly constant, the results are determined only by the height from which the coin falls.']