**Core Concept**
DNA viruses are a group of viruses that have a DNA genome, as opposed to RNA viruses, which have an RNA genome. These viruses can infect a wide range of hosts, from bacteria to humans, and can cause various diseases, including respiratory, gastrointestinal, and skin infections.

**Why the Correct Answer is Right**
Adenoviruses are a type of DNA virus that belongs to the family Adenoviridae. They have a double-stranded DNA genome and can cause a variety of infections, including respiratory tract infections, conjunctivitis, and gastroenteritis. Adenoviruses are highly contagious and can spread through close contact with an infected person or through contaminated surfaces. The virus enters the host cell and replicates its DNA using the host cell's machinery, leading to the production of new viral particles.

**Why Each Wrong Option is Incorrect**
**Option A:** Polio virus is an RNA virus that belongs to the family Picornaviridae. It is a positive-sense single-stranded RNA virus that causes poliomyelitis in humans.
**Option C:** Parvovirus is a small DNA virus that belongs to the family Parvoviridae. However, it is not a member of the adenovirus family and does not have the same range of infections as adenoviruses.
**Option D:** Hepatitis A virus is an RNA virus that belongs to the family Picornaviridae. It is a positive-sense single-stranded RNA virus that causes hepatitis A in humans.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that DNA viruses can be divided into two main groups: those with double-stranded DNA (dsDNA) and those with single-stranded DNA (ssDNA). Adenoviruses are a classic example of dsDNA viruses, while parvoviruses are ssDNA viruses.

**✓ Correct Answer: B. Adenovirus**