**Core Concept**
The intrinsic sympathomimetic activity (ISA) of a beta blocker refers to its partial agonist activity at beta-adrenergic receptors, which can lead to increased heart rate and contractility at lower doses, but reduced efficacy at higher doses. This property is distinct from non-selective beta blockers and beta-1 selective blockers.

**Why the Correct Answer is Right**
The beta blocker with intrinsic sympathomimetic activity (ISA) is **Pindolol**, which has a partial agonist effect at beta-1 adrenergic receptors. This allows it to increase heart rate and contractility, especially at lower doses, making it a useful agent for certain cardiovascular conditions. Pindolol has a unique pharmacological profile that differentiates it from other beta blockers, such as non-selective beta blockers (e.g., Propranolol) and beta-1 selective blockers (e.g., Metoprolol).

**Why Each Wrong Option is Incorrect**
* **Option A:** is incorrect because it does not possess intrinsic sympathomimetic activity.
* **Option B:** is incorrect because it has a different pharmacological profile, lacking ISA.
* **Option D:** is incorrect because it is a non-selective beta blocker without ISA.

**Clinical Pearl / High-Yield Fact**
When choosing a beta blocker for a patient with heart failure, consider the presence of intrinsic sympathomimetic activity (ISA), as beta blockers with ISA (e.g., Pindolol) may provide a more favorable balance between beta-blocking and sympathomimetic effects.

**Correct Answer:** C. Pindolol