Which feature of the lung cell allows oxygen to pass through quickly? choose one answer. a: it is thin b: it has a large nucleus c: it has many mitochondria

You are working in the lab and are working with the same element but with varying isotopes of the element. you are working with c-11, c-13, c-14, and c-15. what is the average atomic mass of this element? (use periodic table) a- 12 b-15 c-14 d-13