**Core Concept:** Cryptococcus is a fungal genus known for causing infections in humans. The question is asking about the least likely site for an infection caused by Cryptococcus.

**Why the Correct Answer is Right:** Cryptococcus neoformans is the most common species responsible for causing infections. It primarily infects the lungs, central nervous system (CNS), and occasionally the skin and bones. Infections in the skin, bones, and soft tissues are uncommon because these tissues are richly supplied with blood and have a robust immune system, making them less susceptible to fungal infections.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Lungs):** Cryptococcus neoformans is commonly found in the lungs of pigeons, bats, and birds, and can cause pulmonary infections in humans. Thus, this option is incorrect.

B. **Option B (Central Nervous System):** Cryptococcus neoformans can invade the bloodstream and reach the CNS, leading to meningitis. This option is incorrect because the correct answer shows that CNS infection is less likely than other sites.

C. **Option C (Skin and Bones):** As mentioned above, skin and bone infections due to Cryptococcus are uncommon due to the robust immune response in these tissues. This option is incorrect.

D. **Option D (Blood):** Cryptococcus neoformans can invade the bloodstream, leading to septicemia and meningitis. Although blood is not affected directly by Cryptococcus, this option is correct because it highlights the way Cryptococcus can cause infection in other organ systems, such as the lungs and CNS.

**Clinical Pearl:** Cryptococcus neoformans infections are often associated with a weakened immune system, especially in HIV/AIDS patients. In immunocompetent individuals, the organism is usually controlled by the immune system and presents as meningitis or pneumonia.

**Correct Answer:** D (Blood): Cryptococcus neoformans can invade the bloodstream, leading to septicemia and meningitis. Although blood is not affected directly by Cryptococcus, this option is correct because it highlights the way Cryptococcus can cause infection in other organ systems, such as the lungs and CNS.