The correct option is A Nerve cells
The tissues which cover or protect the body are called epithelial tissues. Cells of the epithelial tissues are tightly packed and have a small amount of cementing material in between them. These are small cells covering the organs and cavities of the body.
Mast cells are a type of cells belonging to areolar connective tissues. It fills the space around the organs.
Kupffer cells are star-shaped macrophages present in the liver lining.
Nerve cells possess a cell body and one or many thin fiber-like axons. Some nerve cells possess axons as long as 1 meter and thus, are the largest cell in the human body. It is also known as the longest cell in the human body. Thus, the correct answer is option A.