**Core Concept**
Beta-blocker overdose leads to severe bradycardia, hypotension, and potentially life-threatening cardiac complications. In such scenarios, it's crucial to have a treatment strategy that counters the effects of beta-blocker toxicity while stabilizing the cardiovascular system.

**Why the Correct Answer is Right**
In beta-blocker overdose, the primary goal is to restore cardiac function and blood pressure. Atropine is used to counteract the bradycardia caused by beta-blocker toxicity by stimulating the muscarinic receptors in the heart, thereby increasing heart rate. Glucagon acts as a positive inotropic agent, enhancing the contractility of the heart muscle, which helps to counteract the negative inotropic effects of beta-blockers. Calcium chloride is used to help stabilize cardiac membranes and improve cardiac contractility.

**Why Each Wrong Option is Incorrect**
**Option A:** Atropine is used in beta-blocker overdose, but it's not the only treatment. Therefore, option A is incorrect because it doesn't encompass the entire treatment strategy.
**Option B:** Glucagon is indeed used in beta-blocker overdose, but like atropine, it's not the sole treatment. Option B is incorrect because it doesn't account for the other treatment options.
**Option C:** Calcium chloride is used in beta-blocker overdose, but similar to options A and B, it's not the only treatment. Option C is incorrect because it doesn't cover the entire treatment spectrum.

**Clinical Pearl / High-Yield Fact**
In cases of beta-blocker overdose, it's essential to remember that atropine, glucagon, and calcium chloride can be used in combination to effectively manage the cardiovascular complications. This combination is crucial because each agent targets a different aspect of beta-blocker toxicity, allowing for a more comprehensive treatment approach.

**Correct Answer:**
✓ Correct Answer: D. All of these