What does the "r-" represent?

hydrocarbon chain that supports the functional group

the functional group

the radical

none of the above

I think the answer is the first one: "hydrocarbon chain that supports the functional group"

The "R-" represents the hydrocarbon chain that supports the functional group.

B"hf and f-"  is the correct answer took the test on edgenuity and got it right     

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