Which features of alveoli enable them to exchange gases efficiently? (Select all that apply.) small numbers of them in each lung
large surface area
surrounded by blood vessels
thin walls

The third choice .. (:

D)can be increased in a closed system

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf