What is the difference between the independent variable and the control?

Independent variable is a variable changed my the scientist and a control is something kept the same to be compared to the results like for example you want to try a new sauce on a burger you get one group with the sauce the other with the original the original group would be the control.

And a) oxygen i believe

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