I'm struggling with this one too! I disagree with the answer above. If we're talking about a single source charge then zero electric potential would be really far from that charge. We don't just choose where zero electric potential is. It has a formula based on source charge and distance from source charge. I think the key to this question is you could have multiple source charges, e.g. 1 positive source charge and an equal but negative source charge. The point in the middle between those two would be the sum and would be zero. Just because it's zero though, a test charge placed there would move one way or the other (e.g. towards negative source if it's a positive test charge).