**Core Concept**
CMV (Cytomegalovirus) is a type of herpesvirus that belongs to the family of double-stranded DNA viruses. It is a common cause of viral infections, particularly in immunocompromised individuals. CMV can cause a wide range of diseases, from asymptomatic infections to severe illnesses such as retinitis and pneumonitis.

**Why the Correct Answer is Right**
Foscarnet is an antiviral medication that is effective against CMV, but it does not eliminate the virus. Instead, it inhibits viral replication, preventing the virus from causing further damage to the host cells. Foscarnet works by inhibiting viral DNA polymerase, which is essential for the replication of CMV. While foscarnet can reduce viral load and alleviate symptoms, it does not cure the infection, and the virus can remain dormant in the host.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true, as CMV is indeed a double-stranded DNA virus.
**Option B:** This statement is also true, as CMV rarely causes problems in immunocompetent individuals. However, it is worth noting that immunocompetent individuals can still be asymptomatic carriers of CMV.
**Option D:** This statement is true, as CMV retinitis is rare in individuals with a CD4 count >200/mm3, as they have a relatively preserved immune system.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that antiviral medications like foscarnet can only manage CMV infections, not eliminate them. This is particularly important in patients with HIV/AIDS, who may require long-term antiviral therapy to prevent CMV-related complications.

**Correct Answer:** ✓ Correct Answer: C. Foscarnet can eliminate CMV