**Core Concept**
The question is testing the student's understanding of the fundamental difference between viral and bacterial infections in terms of their growth patterns and responses to antibiotics.

**Why the Correct Answer is Right**
Viral infections, unlike bacterial infections, do not respond to antibiotics because they are caused by obligate intracellular parasites. Viruses cannot be killed by antibiotics, which target bacterial cell wall synthesis or protein synthesis. Instead, viral infections are treated with antiviral medications that target specific viral enzymes or processes, such as the replication of viral RNA or DNA.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because antibiotics may not be effective against viral infections, but they are not the primary mechanism by which viral infections are differentiated from bacterial infections.
* **Option B:** This option is incorrect because the presence of a fever is a nonspecific symptom that can occur in both viral and bacterial infections.
* **Option C:** This option is incorrect because the presence of pus is a sign of a bacterial infection, but it is not a characteristic that differentiates viral from bacterial infections.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that viral infections are often treated with antiviral medications rather than antibiotics, and that antibiotics should only be used to treat bacterial infections.

**Correct Answer: D.**