## **Core Concept**
The question tests knowledge of lipoprotein metabolism, specifically the composition of chylomicrons. Chylomicrons are lipoproteins that transport dietary lipids from the intestines to other parts of the body. They are primarily composed of triglycerides and have a specific apolipoprotein profile.

## **Why the Correct Answer is Right**
Apolipoprotein B-48 (**Apo B-48**) is the major apolipoprotein of chylomicrons. It is synthesized in the intestines and plays a critical role in the formation and secretion of chylomicrons. Apo B-48 is essential for the intestinal absorption of lipids and is a key component that distinguishes chylomicrons from other lipoproteins, such as very-low-density lipoproteins (VLDL), which contain Apo B-100.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While Apo A-I is a major apolipoprotein of high-density lipoproteins (HDL), it is also present in chylomicrons but not the major one.
- **Option B:** Apo B-100 is the primary apolipoprotein of low-density lipoproteins (LDL) and VLDL, not chylomicrons.
- **Option D:** Apo E is present in several types of lipoproteins, including chylomicron remnants, but it is not the major apolipoprotein of chylomicrons.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that Apo B-48 is unique to intestinally derived lipoproteins (chylomicrons and their remnants), whereas Apo B-100 is found in liver-derived lipoproteins (VLDL, LDL). This distinction is crucial for understanding lipoprotein metabolism and lipid disorders.

## **Correct Answer:** B. Apo B-48