Answer:
The correct answer is - stoma.
Step-by-step explanation:
Stoma or stomate is a tiny pore that is found on the surface or in the epidermis of the leaf of plants. These tiny pores present all over the leaf and help in the exchange of gases.
The guard cells are present around these pores and help in the opening and closing of these pores. The carbon dioxide is take in and oxygen moves out with the help of these structures and they assist in the process of transpiration.