Determining structure using HNMR and IR
Okay, following up on my comment, I found the spectrum for the "correct" answer:



As you can see in this IR the absorption of the carbonyl peak is shifted down to 1718 as the problem statement claims.

Now, consider this IR spectrum for a conjugated aldehyde which is similar to a conjugated ketone:



In this spectrum, we see that the IR absorption for an aldehyde (normally around 1715) is shifted down below 1700.

Everything else in your answer seems right though. You always need to be careful to consider conjugation when looking at the peak of a carbonyl stretch.

If you want to look around at HNMR/CNMR/IR for basically any reasonable organic molecule, you should check out the SDBS Database. I actually found this to be a useful study tool and just kind of interesting to look around in.