Answer: Choice C

================================================
Step-by-step explanation:
If all the exponents are even, then the polynomial function is even.
- Choice A has a mix of even and odd exponents here, so choice A is neither even nor odd. We can rule this out.
- Choice B is the same story as choice A. So we can rule that out as well.
- Choice C has all of its exponents even. Therefore function C is an even function, and it's the final answer.
- Choice D is the same story as choice A. The only difference is the leading coefficient is positive.