Alveoli are the terminal air sacs of the lungs, and are the sites of gas exchange between the lungs and blood. how does the surface area-to-volume ratio of the cells of alveolar walls relate to their function? hurry.

Which are forms of nitrogen that are usable by humans

Which of these statements best describes the st. lawrence seaway? the st. lawrence seaway connects the st. lawrence river with the arctic ocean. the st. lawrence seaway provides an important trading route between the u. s. and mexico. the st. lawrence seaway provides an important trading route for the u. s, but has little value for canada. the st. lawrence seaway connects the great lakes, the st. lawrence river, and the atlantic ocean.

Number and variety of living organism; includes genetic, species, and ecological types