**Core Concept**
The ear lobule, also known as the ear lobe, is a small, fleshy structure at the bottom of the outer ear. It is composed of skin and underlying connective tissue. The ear lobule plays a crucial role in the overall structure and aesthetic appeal of the ear.

**Why the Correct Answer is Right**
The ear lobule is primarily made up of skin and subcutaneous tissue, which is a layer of connective tissue beneath the skin. This tissue is composed of adipose tissue, fibrous tissue, and blood vessels that supply the ear lobule with oxygen and nutrients. The ear lobule is also attached to the underlying cartilage of the ear through fibrous connections, allowing for its mobility and flexibility.

**Why Each Wrong Option is Incorrect**
**Option A:** Cartilage is a crucial component of the ear's structure, but it is not the primary composition of the ear lobule.
**Option B:** Bone is not a component of the ear lobule, as it is a non-osseous structure.
**Option C:** Muscle is not a primary component of the ear lobule, although there are some small muscle fibers present in the surrounding tissue.

**Clinical Pearl / High-Yield Fact**
The ear lobule is a common site for piercing, and complications such as infection or keloid formation can occur. It is essential to follow proper hygiene and aftercare instructions to minimize the risk of complications.

**Correct Answer: D. Skin and subcutaneous tissue.**