The background has enough highlights and shadows so it gives a good sense of the streaking that gives the feeling of speed.

The legs of the dog are also blurred to give sense of speed yet the face is sharp with mouth open and ears flapping in breeze.

Balance is quite good; you might take a little off the top and right to get more of a feeling of the space which the dog is going to speed through rapidly.

This misses the mark in terms of the assignment. The background is out of focus but not that out of focus. Distracting parts of background are still distracting, for example the horizon across picture. Nothing out of focus in the background focuses attention on the subject

You need to literally be close up to something for this assignment and use a wide open aperture. For example, something small like leafs on a tree, a flower, or a picket fence with only one picket in focus. You want the background not only out of focus, but have the effect of the background out of focus forcing attention to the subject. That clearly doesn't happen in this photograph; it doesn't show selective focus.

This was done with a 50mm lens. A 100mm lens would have eliminated things in background that are distracting.

Interesting photo; in a sense beautiful, yet almost ugly because of debris in the foreground. I suggest that you crop out most of the sky to move the horizon up.

This is a good example to talk about motion in a picture. In a still photograph, the eye does the moving. It moves into the photo, moving about to find the subject. The longer the eye moves about the photo, the more interesting the photo. In this photo, there is opportunity to use motion. Crop to 1/4" from the top of the temple and crop the left to 1/2" - 3/4" of the temple. The eye then moves from lower right, moves in along waterfall, stops at debris, then moves on to the temple. It's the opposite of simplicity, but complexity is not necessarily bad. This is a complex photo. It fulfills the assignment.