**Core Concept**
Cell volume and shape are maintained by a complex interplay of physical forces and biochemical processes. The cell membrane is a semi-permeable lipid bilayer that regulates the movement of ions, water, and other molecules in and out of the cell. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, provides mechanical support and maintains cell shape.

**Why the Correct Answer is Right**
The correct answer is related to the role of the cytoskeleton in maintaining cell shape and volume. Actin filaments and microtubules work together to generate forces that counteract the internal osmotic pressure of the cell. The cytoskeleton also helps to regulate cell volume by controlling the movement of ions and water across the cell membrane. Additionally, the cytoskeleton provides mechanical support by maintaining cell shape and resisting external forces.

**Option A:** This option is incorrect because it does not accurately describe the mechanism by which cell volume and shape are maintained.
**Option B:** This option is incorrect because it refers to the process of cell division, which is not directly related to cell volume and shape maintenance.
**Option C:** This option is incorrect because it refers to the movement of ions and water across the cell membrane, but does not accurately describe the role of the cytoskeleton in maintaining cell shape and volume.

**Clinical Pearl / High-Yield Fact**
The cytoskeleton plays a critical role in maintaining cell shape and volume, and its dysfunction is associated with various diseases, including muscular dystrophy and cancer.

**Correct Answer:** C. Cytoskeleton.