Which of these is different than the others?

Every summer I enter a local photo contest for fun. I happened to notice on the registration form that there was a K-2 category for kids. So I gave Liddy my camera and sent her loose in the backyard. 100 photos later, as I was downloading shots of the ground, flowers, sky, leaves....I notice one photo that is actually pretty good! Jeff and I were laughing because it didn't belong with the others. So for comparison's sake, here are some photos in a row that she took. Can you guess which one we chose to enter?