**Core Concept**
The metabolism of ketone bodies involves a complex series of reactions that occur in the liver, primarily in response to fasting or low carbohydrate intake. The liver plays a crucial role in regulating ketone body production and utilization, which are essential for energy production in various tissues, including the brain and heart.

**Why the Correct Answer is Right**
Ketone bodies are synthesized in the liver from acetyl-CoA through a process involving several key enzymes. The rate-limiting enzyme in this pathway is actually HMG-CoA synthase, not HMG-CoA reductase. HMG-CoA reductase is a key enzyme in the biosynthesis of cholesterol, where it catalyzes the conversion of HMG-CoA to mevalonate. The correct rate-limiting enzyme for ketone body synthesis is HMG-CoA synthase, which facilitates the conversion of acetoacetate to beta-hydroxybutyrate.

**Why Each Wrong Option is Incorrect**
**Option A:** Acetoacetate is indeed one of the primary ketone bodies, but it is not the only one. The other two primary ketone bodies are beta-hydroxybutyrate and acetone.
**Option B:** Ketone bodies are indeed synthesized in the mitochondria of liver cells, where acetyl-CoA is converted to ketone bodies through a series of reactions involving several enzymes.
**Option C:** The liver is indeed the primary site of ketone body synthesis, where acetyl-CoA is converted to ketone bodies in response to fasting or low carbohydrate intake.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that elevated levels of ketone bodies in the blood can indicate diabetic ketoacidosis (DKA), a serious complication of diabetes mellitus. DKA occurs when the body produces high levels of ketones due to a lack of insulin, leading to metabolic acidosis and potentially life-threatening complications.

**✓ Correct Answer: D. HMG CoA reductase is the rate-limiting enzyme**