Fungal infections are difficult to treat because:

• A. Fungi are obligate anaerobes, making them inaccessible to most treatments.
• B. Fungi lack cell walls, so most antibiotics cannot affect them.
• C. Fungi are eukaryotic organisms, making their cells similar to human cells and limiting selective drug targets.
• D. Fungi reproduce only by binary fission, making them resistant to most drugs.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the nature of fungi by recognizing that they are eukaryotic organisms, meaning their cellular structure is more similar to human cells compared to bacteria, which are prokaryotic.
2. Step 2: Recall that many antibiotics target features unique to prokaryotic cells, such as peptidoglycan in bacterial cell walls, which fungi do not have, making those antibiotics ineffective against fungi.
3. Step 3: Note that fungi do have cell walls, but these are composed of different materials (like chitin) than bacterial cell walls, so treatments must target fungal-specific structures without harming human cells.
4. Step 4: Recognize that because fungal cells share many biochemical pathways with human cells, it is challenging to find drugs that selectively target fungi without causing toxicity to human cells.
5. Step 5: Conclude that the difficulty in treating fungal infections arises primarily from the similarity between fungal and human cells, limiting the number of selective drug targets and making treatment more complex.