**Core Concept**
Diplococcus pneumoniae, now known as Streptococcus pneumoniae, is a gram-positive bacterium that is a common cause of pneumonia and other invasive infections. It is characterized by its distinctive diplococcal arrangement, where two cocci are paired together.

**Why the Correct Answer is Right**
The correct answer is related to the characteristics of Diplococcus pneumoniae. This bacterium is known for its ability to form colonies on blood agar that are typically 1-2 mm in diameter, which is smaller than other streptococci. The colonies also exhibit a characteristic "alpha-hemolysis" or partial hemolysis, where the red blood cells are partially broken down, resulting in a greenish discoloration around the colony. Additionally, Diplococcus pneumoniae is a capsulated bacterium, meaning it has a thick polysaccharide capsule that helps it evade the host's immune system.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable as the question does not specify what characteristic is being asked about.
* **Option B:** Incorrect as Diplococcus pneumoniae does not typically exhibit "beta-hemolysis" (complete breakdown of red blood cells) on blood agar.
* **Option C:** Incorrect as Diplococcus pneumoniae is indeed encapsulated, which is a key virulence factor for this bacterium.

**Clinical Pearl / High-Yield Fact**
Diplococcus pneumoniae is a leading cause of community-acquired pneumonia, particularly in older adults and young children, and can cause severe invasive infections such as meningitis and bacteremia.

**Correct Answer: B. Beta-hemolysis is not a characteristic of Diplococcus pneumoniae.**