When my daughter was little, we purchased a book on dinosaurs which came with several plastic toy dinosaurs. As an activity, she would group the dinosaurs in a certain way and we would guess the reason behind the grouping. For example, she would group the dinosaurs that had spikes on their backs and those without. When we guessed correctly, it would be our turn to group the dinosaurs and she would guess the reason for the grouping. We liked this activity because of the conversations we would have with her, which helped to enrich her vocabulary. Sometimes, we even failed to guess her reasoning.
The pdf file below has four worksheets which ask the student to color or circle the object or animal that does not belong in the group. I posted similar worksheets in 2013. I made some changes to those worksheets. All illustrations are by samutsamot_mom, except for the images for the three dogs, deer, and fish, which were obtained from clker.com.
If you are homeschooling your child, it is best to work on these sheets with them so that you will know his or her reason for choosing a certain object from the group.
Click on the link, not the thumbnails, to open the file.