Transitional fossils. There aren't any. At all.
Or, you could point to the fact that a wing is either a wing or it isn't a wing, there is no in-between. And those which would possess such a deformity would die off.
The most effective are that of form/essence, if someone has a little philosophical knowledge. A dog is a dog and only produces dogs, it never turns into a cat or a lizard, because then it would cease to be a dog.
I know there are a lot of problems with the Dimonds, but in the video
Creation and Miracles --- an excellent resource! --- our friend Brother Michael points out that similarity of design and function between certain aspects of species does not necessarily denote a common
origin, but points more towards a common
designer.
Word to the wise, if you are homeschooling and want to use a secular text, the Holt
Life Science book presents such a weak case for evolution, that I have to suspect it is deliberately denatured to make the text palatable to conservative school boards and state departments of education, maybe such as Texas, eh? I have been able to take that text, and while using it, and being able to docuмent with written work and tests that we have been using it (in case we would ever be called upon to defend our homeschool, grading, etc.), you can poke holes straight through their treatment of evolution. I told my son that it would take more faith to believe in evolution, than to believe in creation!
Holt has outstanding CD-ROM-based resources, all the exercises and tests you could want, it is totally "turn-key". We used the Apologia Press
Understanding Creation series for chemistry and physics, but I find the Charlotte Mason approach kind of puerile and low on solid scientific facts. We will find better texts for the remaining high school grades. And it comes with no resources, you have to make your own or rely on free-standing online sources.