According to O'Brien, after he had broken Jones, Aaronson, and Ritherford down, what was the only thing left inside of them:

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is

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   

C) the increase in atmospheric pressure pushes the walls of the balloon outward thus making it  is the answer.hope i you.