Answer: cell wall
Explanation: a cell wall is a complex protective structure which gives shape and protection to a plant cell.
Among the functions of a cell wall is maintaining the structural integrity of a cell and providing strength. Because a cell wall has semi-permeable outer layer, it filters molecules that pass in and out of the cell hence, acting as a defense structure against a variety of external factors. It has pores and receptors that regulate various functions of the cell.
