**Core Concept**
Cholesterol Ester Transfer Protein (CETP) plays a crucial role in the transfer of lipids between high-density lipoproteins (HDL) and low-density lipoproteins (LDL) or very-low-density lipoproteins (VLDL). This protein is essential for maintaining lipid homeostasis in the body.

**Why the Correct Answer is Right**
The correct answer is D. Facilitates the transfer of triacylglycerol from HDL to LDL. CETP facilitates the transfer of cholesterol esters from HDL to LDL (or VLDL) in exchange for triacylglycerols. This process is essential for maintaining the balance of cholesterol and triacylglycerol in the body. The transfer of triacylglycerol from HDL to LDL is a critical step in this process, as it allows for the redistribution of lipids from HDL (often referred to as "good cholesterol") to LDL (often referred to as "bad cholesterol").

**Why Each Wrong Option is Incorrect**
* **Option A:** Associated with HDL - This statement is true, as CETP is indeed associated with HDL. CETP binds to HDL and facilitates the transfer of lipids.
* **Option B:** Facilitates the transfer of cholesterol ester from HDL to LDL - This statement is true and describes the primary function of CETP.
* **Option D:** Facilitates the transfer of triacylglycerol from HDL to LDL - This is the correct answer, but we've already explained why.

**Clinical Pearl / High-Yield Fact**
CETP is a key player in lipid metabolism, and its activity has been linked to cardiovascular disease. Elevated CETP levels have been associated with increased risk of atherosclerosis, highlighting the importance of maintaining lipid balance in the body.

**Correct Answer Line**
✓ Correct Answer: D. Facilitates the transfer of triacylglycerol from HDL to LDL.