Which structure allow the flow of gases in and out of a leaf

The correct answer is stomata.

Explanation:

The leaf structure is adapted for gas exchange between plants and the environment. The cells in the spongy mesophyll have tiny pores, termed as stomata, present in the leaf surface. Most of the stomata are found in the lower epidermis. These tiny pores control gas exchange. Opening and closing of stomata depend on the guard cell turgidity.

Diffusion of oxygen, carbon dioxide and water vapor in and out of the leaf is highest when these stomata are open.

Thus, the correct answer is stomata.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

i think that it is plants