**Core Concept**
High anion gap metabolic acidosis (HAGMA) is a condition characterized by an increase in the anion gap, typically above 12, due to the accumulation of unmeasured anions. This can result from various causes, including lactic acidosis, ketoacidosis, and certain medications.

**Why the Correct Answer is Right**
In this scenario, the patient developed high anion gap metabolic acidosis with increased serum lactate after receiving Linezolid. Linezolid is an antibiotic that can cause lactic acidosis as a side effect. Lactic acidosis is characterized by an increase in serum lactate levels, which is consistent with the patient's presentation. The negative ketone result rules out diabetic ketoacidosis. The combination of high anion gap metabolic acidosis, increased serum lactate, and negative ketone is most consistent with lactic acidosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the scenario, as lactic acidosis is not typically associated with a mixed acid-base disorder.

**Option B:** Diabetic ketoacidosis would typically present with a positive ketone result, which is not the case in this scenario.

**Option C:** This option is incorrect, as the patient's presentation is not consistent with a non-anion gap metabolic acidosis, which is typically seen in conditions such as hyperchloremic metabolic acidosis.

**Option D:** This option is not relevant to the scenario, as the patient's presentation is not consistent with a respiratory acidosis.

**Clinical Pearl / High-Yield Fact**
Linezolid-induced lactic acidosis is a rare but serious side effect that can occur in patients receiving this antibiotic. It is essential to monitor patients for signs of lactic acidosis, such as increased serum lactate levels and high anion gap metabolic acidosis.

**Correct Answer:** B. Diabetic ketoacidosis is typically characterized by a positive ketone result, which is not the case in this scenario.