Brent provided a nice solution, but there's also an easy way to GUESS on this problem:
Since h is not the radius but is perpendicular to the diameter, we can infer that it's shorter than the radius:
Therefore, we can eliminate E.
We can also infer that h must be greater than 4, since the angle that's across from must be greater than 45 degrees. Compare these two:
We don't have to calculate the angle of x to see that it's opening wider than 45*. Thus angle y must be less than 45 degrees. Since larger sides are across from larger angles, h must be larger than 4.
Eliminate any answer choices less than 4: A, B, and C.
The only thing left must be the answer:
D.
