It would be Benzophenone
So Benzophenone as well would be in my crude material! Wow, so there are a lot of different compounds in my crude material!!
There could well be! That's one of the things that makes organic chemistry and especially reaction workups interesting...
My guess would be that the compounds your professor expected you to recognize as possible impurities would be those that you knew had to be in your reaction at one point or another, like the starting materials, intermediates, solvents, and workup products, rather than the side products which you might or might not expect to find based on your conditions, like the CO2
coupling with the grignard, or the grignard self-coupling. So at a minimum, you might expect to see ethyl ether, methyl benzoate, bromobenzene, benzene, benzophenone, and your product. That's five extra compounds instead of four, but maybe he wasn't considering solvent as an extra compound?