**Core Concept**
Pneumococci, or *Streptococcus pneumoniae*, are **Gram-positive** cocci that play a significant role in respiratory infections, particularly **pneumonia**. They have a **polysaccharide capsule** that aids in virulence and evasion of the host immune system.

**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the general characteristics of pneumococci. Pneumococci are known for their ability to cause invasive diseases such as **bacteremia**, **meningitis**, and **pneumonia**, especially in individuals with compromised immune systems. They are typically **facultative anaerobes** and can be found in the **upper respiratory tract** of healthy individuals.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific details of option A, we cannot directly address why it is incorrect. However, if it pertains to pneumococci being **anaerobic**, this would be incorrect because pneumococci are **facultative anaerobes**.
**Option B:** Similarly, without specifics, if option B suggests pneumococci are **Gram-negative**, this is incorrect because pneumococci are **Gram-positive**.
**Option C:** If option C implies pneumococci do not have a **capsule**, this is incorrect because the **polysaccharide capsule** is a key virulence factor.
**Option D:** If option D states pneumococci are not a common cause of **community-acquired pneumonia**, this would be incorrect as pneumococci are indeed a leading cause.

**Clinical Pearl / High-Yield Fact**
A crucial point to remember is that pneumococcal infections can be prevented with **vaccination**, particularly in high-risk populations such as the elderly and young children. The **pneumococcal conjugate vaccine** is effective against invasive pneumococcal disease.

**Correct Answer:** Correct Answer: D. Pneumococci are often resistant to penicillin.