Final answer:
Option d, 'Cell wall: helps shape the cell,' correctly describes a specific structure and function within plant cells, which provides support, protection, and maintains shape.
Step-by-step explanation:
The question is asking to identify which plant cell structure is described correctly in relation to its specific function. Among the options, d. Cell wall: helps shape the cell correctly describes a structure that is specific to plant cells and not typically found in animal cells. The cell wall is a rigid layer that is located outside the cell membrane. This structure provides protection, structural support, and maintains the shape of the cell. It is composed mainly of cellulose and may include lignin to make it more rigid. This characteristic enables the plant cell to withstand the turgor pressure that results from the water inside the cell, thus contributing to the plant's overall rigidity and structure.
Plant cells contain additional structures not found in animal cells, such as a large central vacuole, which stores water and dissolved substances to maintain pressure against the cell wall, and plastids such as chloroplasts for photosynthesis. While both plant and animal cells have a nucleus which acts as the control center of the cell and contains genetic material, the nucleus does not hold water nor does it provide support, which rules out options a and b. Similarly, the cell membrane is not primarily responsible for providing support, eliminating option c as the correct answer.