Which reaction would most likely occur at the cathode of an electrochemical cell?

Bthats what im doing to and i figured it out it is b

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   

Answer/nitrogen compounds in the soil;