The outermost layer of plant stems in dicotyledons consists of epidermal cells and guard cells that surround openings called stomata.
The epidermal cells are usually covered with a waterproof layer that provides protection from injury and water loss. The stomata allow gas exchange. The epidermal cells and stomata have functions similar to those of which two human body systems?

a. skeletal and respiratory
b. cardiovascular and skeletal
c. integumentary and respiratory
d. cardiovascular and integumentary