The correct answer is option 4, Humans.

Option 1, Bacteria: Bacteria have cell walls made up of peptidoglycan, a unique material not found in other organisms. This cell wall provides structure and support to the bacterium.

Option 2, Plants: Plants do have cell walls composed mainly of cellulose. The cell wall is a rigid layer outside the plasma membrane and provides support and protection for plant cells.

Option 3, Fungi: Fungi also have cell walls, although they are composed of a different material called chitin. The cell wall in fungi provides structural support and protection.

Option 4, Humans: Humans do not have cell walls. Instead, human cells are surrounded by a plasma membrane, which separates the cell`s internal components from the external environment. The plasma membrane regulates the movement of substances in and out of the cell, but it does not provide the same rigid support as a cell wall.

Therefore, the correct answer is option 4, Humans, as they do not possess a cell wall.