**Core Concept**
The question is testing the student's knowledge of pathogenic organisms that exhibit temperature-dependent motility, a characteristic feature of certain bacteria. This phenomenon is often associated with the ability of these organisms to invade host tissues.

**Why the Correct Answer is Right**
The correct answer is an example of a pathogenic bacterium that undergoes temperature-dependent motility. At 25°C, this bacterium is motile due to its ability to polymerize actin, a process known as actin-based motility. This mechanism allows the bacterium to move within the host's tissues. However, at 37°C, the bacterium becomes non-motile, likely due to changes in its membrane or cytoskeleton that inhibit actin polymerization. The bacterium's ability to invade host tissues is a key virulence factor.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it refers to a different type of pathogenic bacterium that does not exhibit temperature-dependent motility.
* **Option B:** This option is incorrect because it refers to a bacterium that does not use actin-based motility to escape host defenses.
* **Option C:** This option is incorrect because it refers to a bacterium that is always motile at both 25°C and 37°C, and does not exhibit temperature-dependent motility.

**Clinical Pearl / High-Yield Fact**
The ability of certain bacteria to exhibit temperature-dependent motility is a key virulence factor that allows them to invade host tissues and cause disease. This phenomenon is often associated with the ability of these organisms to use actin-based motility to move within the host's tissues.

**Correct Answer:** C. Listeria monocytogenes