The second you uttered that, I'd thank you for your time and walk out.

What on earth does that have to do with building (actually, in most cases, maintaining) a CRUD web app?

What does that have to do with n-tier web application architecture?

Is that a real question? I too would refuse that in a programmer interview, unless it was joke. Of course the answer is white - polar bear and you are at the north pole. Even as a puzzle question it's pretty lame. Still puzzling over the boiling bagels on Mars one...