**Core Concept**
Methemoglobinemia is a condition characterized by an abnormal amount of methemoglobin in the blood, which can lead to tissue hypoxia. Local anesthetics can cause methemoglobinemia through various mechanisms, including the oxidation of hemoglobin to methemoglobin. Prilocaine is known to be metabolized to o-toluidine, which is a potent oxidizing agent that can cause methemoglobinemia.

**Why the Correct Answer is Right**
Prilocaine is metabolized by the enzyme xanthine oxidase to o-toluidine, a compound that can oxidize hemoglobin to methemoglobin. This is a well-documented side effect of prilocaine, and it is the primary reason why prilocaine is associated with methemoglobinemia. The incidence of methemoglobinemia is higher with prilocaine than with other local anesthetics, making it a significant concern in clinical practice.

**Why Each Wrong Option is Incorrect**
**Option A:** Procaine is a local anesthetic that is metabolized by plasma cholinesterase, and it is not associated with methemoglobinemia.
**Option C:** Etidocaine is a long-acting local anesthetic that is metabolized by the liver, and it does not have a significant association with methemoglobinemia.
**Option D:** Ropivacaine is a modern local anesthetic that is metabolized by the liver, and it does not have a significant association with methemoglobinemia.

**Clinical Pearl / High-Yield Fact**
Prilocaine-induced methemoglobinemia is more common in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, as these patients have decreased levels of the enzyme responsible for protecting against oxidative stress.

**✓ Correct Answer: B. Prilocaine**