The others posters in this thread have properly solved the problem, so I won't rehash any of that work here. Instead, I want to point out some details on the "nature" of DS questions. DS questions are on the GMAT to test you on a variety of skills that are not strictly "math skills": organization, accuracy, attention-to-detail, thoroughness, the ability to PROVE that you're correct, etc.
Every DS question has AT LEAST one answer. Part of your job when facing any DS question is to look "beyond" the obvious. To get the points, you have to show how thorough your thinking is by finding the alternatives (if they exist).
In Fact 2, I'm sure that almost everyone would think "oh, it has to be the number 1...."; if those same Test Takers don't do the necessary extra work to realize that 0 is ALSO a possible answer, then those same people will get this easy question wrong, lose out on those points and not even know it. Get in the habit of thinking - do work, take notes, consider the possibilities and you'd be amazed how easy most DS questions actually are.
GMAT assassins aren't born, they're made,
Official Guide 2016 Question Breakdown:
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