Thanks for the critiques, and yes, it's not an easy problem.
There are countermeasures. For instance, who said we'll let you see the whole question bank? And if you type a close enough approximation, out come the plagiarism checkers.
But when somebody's gone to the trouble to make a database online of every problem, I'm happy, because if that's so we must be successful enough that we have plenty more resources to game their gaming.