Practice question

Pick C: K+. Thinking about Action potential in a practical way — what the structure does, or what the process achieves — leads you here. Clinically and academically, the same logic shows up again and again: cause and effect line up with K+ — that is the mechanism or reason the stem is pointing to. Hence K+ is correct. Treat this as a building block for the rest of Action potential; neighbouring topics often reuse the same principle. Keep a one-line summary card for this idea and revisit it before the paper; short, repeated review beats long cramming sessions. If the wording feels dense, translate it into everyday language first, then map that plain sentence back onto K+.