Which of the following provides structural support in plants, fungi, and bacteria?

The cell wall is the correct answer because it serves as a rigid outer layer that provides structural support and protection for the cells of plants, fungi, and bacteria. In plants, the cell wall is primarily composed of cellulose, which helps maintain cell shape and withstand internal pressure from turgor. In fungi, the cell wall is primarily made of chitin, which gives strength and rigidity. Bacteria have a cell wall made of peptidoglycan, which provides additional protection and structure.

Other options, while essential for cellular functions, do not provide structural support in the same way. The cytoplasm is the semi-fluid substance within the cell where organelles are suspended but does not provide external support. The plasma membrane, although critical for regulating the movement of substances in and out of the cell and maintaining homeostasis, is a flexible barrier rather than a rigid structure. Ribosomes are involved in protein synthesis and do not contribute to structural integrity.