"A plant system must balance its need for water with its need for carbon dioxide and oxygen. If too much water is lost, the stomata will close. How does this affect a plant's ability to regulate levels of carbon dioxide and oxygen?"

Guard cells

Explanation:

Guard cells are the cells that are found around the openings of the stomata, their functions is that they regulate the opening and closing of the stomata. These cells are always fill with latex which is of high percentage of water, therefore when the intake of water is low, the functionality of the cells will be affected.

And it must be noted that, the stomata is very important in the exchange of gases, that is a process where oxygen is released and carbon dioxide is absorbed. Therefore when the cells are affected, the gas exchange will also be effected.

i think it’s c but i might be wrong. if i am let me know! have a good rest of your day as well!