**Core Concept:** Atherosclerosis is a chronic inflammatory disease involving the arterial walls, leading to the formation of atherosclerotic plaques. These plaques consist of various components that contribute to their composition and progression.

**Why the Correct Answer is Right:** The correct answer, **D**, is based on the understanding of the principal components of atherosclerotic plaques. These plaques are primarily composed of lipids (fatty streaks), macrophages (foam cells), smooth muscle cells, extracellular matrix, and calcium deposition.

**Why Each Wrong Option is Incorrect:** Let's analyze the other options:

**Option A:** Calcium deposition is a significant component of atherosclerotic plaques, contributing to plaque stability and progression. Therefore, this is incorrect.

**Option B:** Smooth muscle cells are a crucial component of the plaque, helping to form the fibrous cap and contribute to plaque stability. This is incorrect as well.

**Option C:** Macrophages (foam cells) are essential in the initial stages of atherosclerosis, engulfing lipids and contributing to plaque formation. This is incorrect.

**Option D:** Lipids (fatty streaks) are the primary component of early atherosclerotic plaques, providing a scaffold for other cells to accumulate. This is the correct answer.

**Clinical Pearl:** In the context of this question, it highlights the importance of understanding the principal components of atherosclerotic plaques and their roles in plaque formation and progression. Atherosclerosis is a complex process involving multiple cellular and molecular components, and identifying the correct answers requires a thorough understanding of the disease process.