Correct Answer: Subsidiary cells

Solution : The correct option is Subsidiary cells.

Subsidiary cells are specialised plant cells that interact with guard cells, most especially in the stomatal complexes. A stomatal complex is made up of two guard cells bordered by one or more subsidiary cells. The subsidiary cells perform critical functions in the regulation of stomatal openings and closings, which govern the exchange of gases (such as carbon dioxide and oxygen) and water vapour between the plant and the surrounding environment.