Consider that choice B is the same as saying 2x^2+1x^0.
The exponents 2 and 0 are both even, which is sufficient to say that the entire polynomial function itself is also even.
Something like choice A expands out and simplifies to x^2-2x+2, and that's equivalent to saying x^2+2x^1+2x^0. The presence of the x^1 term, with its odd exponent, is what makes choice A not even (it's not odd either).
Similarly, choices C and D also have exponents of 1, so they aren't even either.
