What is the electron shielding effect? What is the trend for it? How and why does it happen?

Do u have the n? or maybe the m?

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   

The answer to your question would be c. mineral oil