Explanation:

- Sperm: These are among the smallest cells in the human body. Their main job is to deliver genetic material to the egg.

- Ovum: The ovum, or egg cell, is indeed the largest cell in the human body. It is visible to the naked eye and plays a crucial role in reproduction.

- Ovum is the correct answer.

- Neurons: These can be very long, with some stretching up to a meter in length, but their overall volume is not as large as the ovum.

- Osteoclast: These are large cells that help break down bone tissue, but they are not as large as an ovum.