Question

which of these cells of the dermal tissue of plants prevent water loss and control gas exchange?
phloem cells
companion cells
parenchyma cells
guard cells

Explanation:

Phloem cells transport organic nutrients; companion cells support phloem function; parenchyma cells store food and carry out metabolic functions. Guard cells surround stomata, opening/closing them to regulate gas exchange and reduce water loss.

Answer:

guard cells