**Core Concept**
Mumps is a viral infection caused by the mumps virus (MuV), primarily affecting the salivary glands and leading to symptoms like parotitis, fever, and swelling of the face. The virus spreads through respiratory droplets and close contact with an infected individual.

**Why the Correct Answer is Right**
Mumps virus multiplies in the respiratory epithelium, but it primarily targets the salivary glands, particularly the parotid glands. The correct pathogenesis involves the virus spreading to the parotid glands via the auriculotemporal nerve, not through Stenson's duct. Stenson's duct is the pathway through which saliva from the parotid gland flows into the oral cavity, but it is not the primary route of viral entry.

**Why Each Wrong Option is Incorrect**
**Option A:** The incubation period of mumps is indeed 18-21 days, which makes this statement true.
**Option B:** While tissue damage is a consequence of the infection, it is not a defining characteristic of mumps. Mumps primarily causes inflammation and swelling of the salivary glands.
**Option C:** The mumps virus does multiply in the respiratory epithelium, which is a critical step in the viral life cycle.

**Clinical Pearl / High-Yield Fact**
Mumps is a vaccine-preventable disease, and the MMR vaccine (measles, mumps, and rubella) is highly effective in preventing mumps infection. Mumps vaccination is a critical component of childhood immunization schedules worldwide.

**✓ Correct Answer: D. Spreads through Stenson's duct to Parotid gland**