First I should note this is really quite an evil question pretending to be a simple one. I thought I understood EV myself until I looked at this question.

1. We need to look closely at exactly what is going on here with each of the four answers. The first question is, where exactly did we get these measures from in the first place. In particular the BAC - we got the BAC by performing an 'Expert Analysis' from the most accurate source of information available to us at the time. Those are the estimates provided not by the PM but by the interview with the person responsible for performing each of the WBS packages (also known as bottom up analysis). Bear in mind GIGO - garbage in garbage out.

2. Also note that BAC is simply a rollup of PV - it's the sum of the those WBS estimated values we estimated above. Now we know that both PV and BAC are A). The same thing and B.) Simply estimates.

3. Note that EAC is a derived number - derived from what? Derived from our potentially innacurate cost estimates.

Despite the amount of words expended, i have really only made one point - that our estimates all rely on assumptions.

Ok so now lets look at the question: We know now that it's all about the data that originally went into the estimates in the first place. What do we call this - we call it the bottom up estimate. And so per PMI, the correct thing to do is to go back to your WBS and do better what you did originally wrong.

Hope it helps - it helped me to think it through.