Yes
@aldol16 is right (although I think you might've switched "depolarized" and "hyperpolarized")! The key is understanding what "command potential" is (it's related to patch clamping, which is a cool neuroscience topic). The command potential is like a "set value" for the membrane potential - the apparatus basically ensures that the neuron remains "stuck" at that potential by manipulating the current. In this manner, the apparatus can indirectly measure what actual changes are taking place within the cell.
For example, let's say a cell is resting at a potential equal to the command. If the system suddenly has to put in a certain amount of current to maintain the command potential, we know that some change must've just occurred to hyperpolarize the cell - AND we can use the amount of current put in to find out the extent of this hyperpolarization. Also, going back to your question -
if I remember correctly, this question is complicated by the fact that the passage treats -60 mV as resting potential (not -70 mV).
But returning to the idea of command potential, we can see that the question wasn't talking about a transition from -70 mV to -60 mV. If it were, you'd be right - that would certainly require positive ions to enter the cell, or negative ions to exit. But instead, it's saying that the cell WAS previously held at the command potential (-60 mV, which is the same as the resting potential that they cite), but some change caused it to deviate from that value. In particular,
something happened that made it more negative (hyperpolarized), which is why we then needed to add +3 mA of current to bring it BACK up to that -60 mV value. The only answer that matches that assessment is B - positive ions flowed out of the cell, so we needed to send in some more current to bring the cell up to its previous potential.
Hope that helps a bit!
