## Core Concept
Infectious mononucleosis, also known as glandular fever, is a condition caused by the Epstein-Barr virus (EBV). It primarily affects the lymphoid system and can lead to symptoms such as fever, sore throat, lymphadenopathy, and fatigue. The diagnosis often involves serological tests to detect antibodies against EBV.

## Why the Correct Answer is Right
The correct statement about infectious mononucleosis is related to its causative agent and clinical manifestations. EBV infects B lymphocytes, leading to their proliferation. This results in the characteristic symptoms and laboratory findings of the disease, including the presence of atypical lymphocytes in the blood.

## Why Each Wrong Option is Incorrect
- **Option A:** Typically, infectious mononucleosis is characterized by an increase in white blood cell count, often with a predominance of lymphocytes, and the presence of atypical lymphocytes. A statement suggesting a decrease in white blood cell count or absence of atypical lymphocytes would be incorrect.
- **Option B:** If a statement claims that EBV primarily infects T lymphocytes, it would be incorrect because EBV primarily infects B lymphocytes.
- **Option C:** A claim that the disease does not cause sore throat or lymphadenopathy would be incorrect as these are common symptoms.
- **Option D:** Without specific details on option D, we proceed with the understanding that the correct answer relates to a false statement about infectious mononucleosis.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that patients with infectious mononucleosis should avoid contact sports for at least 2 weeks after the onset of illness due to the risk of splenic rupture. This condition is also known for causing a false-positive result in some rapid plasma reagin (RPR) tests for syphilis due to the presence of heterophile antibodies.

## Correct Answer: D.