That is a gorgeous nature shot. The detail on the duck is awesome and the water drops coming off it's nose are neat.

There is some very subtle selective focus here, but I think they are looking for pound-you-over-the-head selective focus for this theme.

You've got a good depth of field, but selective focus means (to me, anyway) a very, very narrow depth of field to accentuate a particular part of your composition. This is a very nice image, but other compositional elements are creating the subject focus, not a narrow DOF.

Doesn't have much of an impact for me subject wise. The grass/brush stems are a bit distracting and I wish the ducks eye was open.