Which statement best describes the human respiratory system? A) It is composed of a network of moist passageways that permit air to flow from the external environment to the lungs. B) Each cell of the human body is in direct contact with the external environment, and gas exchange occurs by diffusion. C) The external body surface is kept moist to allow for gas exchange. D) Gases diffuse across membranes on both the external and internal surfaces of the body.

d

Explanation:because you want my d

A) It is composed of a network of moist passageways that permit air to flow from the external environment to the lungs.

Explanation:

the food storage products of chrysophytes are oils or the polysaccharide laminarin.   formerly classified as plants, the chrysophytes contain the photosynthetic pigments chlorophyll a and c all but the yellow-green algae also contain the carotenoid pigment fucoxanthin.

the atmospheric gas that forms a mild acid when dissolved in water is called carbon dioxide. the correct answer is a. 2.) chemical weathering would cause an inscription on a marble headstone to become harder and harder to read over time.