**Core Concept:** The external auditory canal is a part of the ear that connects the pinnae (earlobes) to the tympanic membrane (eardrum). It is lined with stratified squamous epithelium and mostly composed of cartilage.

**Why the Correct Answer is Right:** The correct answer is "D," which states that the cartilagenous part of the external auditory canal is made up of elastic cartilage. Elastic cartilage is a type of cartilage that maintains its shape when deformed, making it ideal for structures that require flexibility, such as the external auditory canal. This type of cartilage contains collagen fibers arranged in a specific pattern, allowing it to return to its original shape after being deformed.

**Why Each Wrong Option is Incorrect:**

A. Collagenous cartilage (also known as fibrocartilage) is too rigid, making it unsuitable for the flexible structure of the external auditory canal.

B. The correct answer is not fibroosseous cartilage, which is a combination of bone and cartilage found in certain joints and not relevant to the external auditory canal.

C. The correct answer is not fibromucosal cartilage, which is a type of cartilage found in the trachea and not relevant to the external auditory canal.

**Clinical Pearl / High-Yield Fact:** The presence of elastic cartilage in the external auditory canal is essential for its functionality, as it allows the canal to maintain its shape while also being flexible enough to prevent the entry of water and debris into the inner ear during swimming or bathing.

**Correct Answer:** D. Elastic cartilage