**Core Concept**
Diphtheria carriers are individuals who harbor the bacterium Corynebacterium diphtheriae in their respiratory tract, but do not exhibit symptoms of the disease themselves. However, they can transmit the bacteria to others, potentially leading to outbreaks.

**Why the Correct Answer is Right**
Diphtheria carriers are typically asymptomatic, but they can still shed the bacteria through respiratory secretions. The presence of the bacteria in the throat can be detected through cultures. These carriers are often identified during outbreaks or when they are in close contact with susceptible individuals, such as newborns or individuals with compromised immune systems.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because diphtheria carriers can indeed harbor the bacteria in their respiratory tract, even if they do not exhibit symptoms.
**Option B:** This statement is incorrect because diphtheria carriers can shed the bacteria through respiratory secretions, potentially infecting others.
**Option C:** This statement is incorrect because diphtheria carriers can still transmit the bacteria to others, even if they do not appear to be sick themselves.

**Clinical Pearl / High-Yield Fact**
Diphtheria carriers can be identified through throat cultures and are often targeted for treatment and isolation to prevent further transmission.

**Correct Answer:** C. Diphtheria carriers are typically symptomatic.