Final answer:
Stomata are the structures in a leaf that allow for gas exchange with the atmosphere, regulated by guard cells.answer is option B.
Step-by-step explanation:
The structure responsible for gas exchange between the tissues of a leaf and the atmosphere is the stomata. These are small openings usually found on the underside of the leaf. Each stoma is surrounded by a pair of guard cells that regulate its opening and closing, facilitating the intake of carbon dioxide and the release of oxygen and water vapor necessary for photosynthesis.
The epidermis serves as a protective layer and secretes a cuticle to prevent water loss, while the vascular bundle, consisting of the xylem and phloem, is responsible for the transport of water, nutrients, and sugars, not for gas exchange.