## Core Concept
The question tests knowledge of the characteristics of paramyxoviruses, specifically their surface proteins. Paramyxoviruses are a family of RNA viruses that include several important human and animal pathogens. They are characterized by their envelope and two main types of surface proteins: hemagglutinin-neuraminidase (HN) and fusion (F) proteins.

## Why the Correct Answer is Right
The correct answer, , refers to the Mumps virus. Mumps virus is a paramyxovirus that causes mumps, a contagious infection primarily affecting the salivary glands near the ears, leading to symptoms like swelling in these areas. Unlike other paramyxoviruses such as Sendai virus, Newcastle disease virus, and some others that have both hemagglutinin and neuraminidase activities in their HN protein, the Mumps virus indeed possesses hemagglutinin but lacks neuraminidase activity. However, another key point here is understanding which viruses are known for lacking both or having a unique characteristic.

## Why Each Wrong Option is Incorrect
- **Option A:** - This option might refer to a virus with both activities, which does not match the criteria given.
- **Option B:** - This could potentially refer to another virus with different properties.
- **Option D:** - This option might represent a virus known to have both hemagglutinin and neuraminidase activities.

## Clinical Pearl / High-Yield Fact
A key point to remember is that while many paramyxoviruses have a hemagglutinin-neuraminidase (HN) protein that exhibits both hemagglutinin and neuraminidase activities, the question specifically asks for a virus lacking both. Mumps virus indeed has hemagglutinin activity but is noted for not having neuraminidase activity like some others. This question tests the specificity of viral characteristics.

## Correct Answer Line
**Correct Answer: C. Mumps virus**