**Core Concept**
Pneumococcus, also known as Streptococcus pneumoniae, is a Gram-positive bacterium that is a primary cause of pneumonia, meningitis, and other invasive infections. The bacterium has a polysaccharide capsule that plays a crucial role in its virulence and evasion of host immune responses.

**Why the Correct Answer is Right**
The correct answer will be a statement that accurately describes a characteristic of Pneumococcus. The polysaccharide capsule of Pneumococcus is a key virulence factor, as it prevents phagocytosis by host immune cells. The capsule is composed of a variety of polysaccharides, including those of types 1, 2, and 3, which are commonly associated with invasive disease. The capsule is also the basis for the Pneumococcal Conjugate Vaccine (PCV), which is used to prevent invasive Pneumococcal disease.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe a characteristic of Pneumococcus.
* **Option B:** This option is incorrect because it does not accurately describe a characteristic of Pneumococcus.
* **Option D:** This option is incorrect because it does not accurately describe a characteristic of Pneumococcus.

**Clinical Pearl / High-Yield Fact**
Pneumococcus is a leading cause of pneumonia, meningitis, and other invasive infections in adults and children worldwide. The polysaccharide capsule of Pneumococcus is a key virulence factor, and the Pneumococcal Conjugate Vaccine (PCV) is an effective tool for preventing invasive Pneumococcal disease.

**Correct Answer:** D.