**Core Concept**
Rabies is a fatal viral disease transmitted through the saliva of infected mammals, primarily through bites. The virus targets the central nervous system, causing inflammation of the brain, which ultimately leads to death. Prompt post-exposure prophylaxis (PEP) is crucial to prevent the disease.

**Why the Correct Answer is Right**
The correct answer is the immediate administration of rabies immune globulin (RIG) and rabies vaccine. RIG provides immediate, passive immunity against the virus, while the vaccine stimulates the production of antibodies to fight the virus. The combination of RIG and vaccine is the most effective PEP regimen, significantly reducing the risk of developing rabies after a bite from an infected animal. The administration of RIG and vaccine should occur as soon as possible after the bite, ideally within 48 hours.

**Why Each Wrong Option is Incorrect**
**Option A:** Broad-spectrum antibiotics are ineffective against viral infections like rabies. They may be used to treat secondary bacterial infections but do not prevent the progression of rabies.

**Option B:** High-dose acyclovir is an antiviral medication used to treat herpesvirus infections, not rabies. It is not indicated for post-exposure prophylaxis against rabies.

**Option C:** IV ribavirin is an antiviral medication used to treat certain viral infections, such as respiratory syncytial virus (RSV) and hepatitis C. It is not effective against rabies and is not indicated for post-exposure prophylaxis.

**Clinical Pearl / High-Yield Fact**
The key to preventing rabies is prompt administration of PEP, ideally within 48 hours of the bite. Delaying treatment can significantly reduce the effectiveness of PEP and increase the risk of developing the disease.

**✓ Correct Answer:** D. Rabies immune globulin plus rabies vaccine