Cellular work is carried out by a. the different types of molecules that the cell assembles. b. organisms that have a symbiotic relationship with the cell. c. energy-deficient compounds. d. only nucleic acids, such as dna and rna.

Cellular work is carried out by the different types of molecules that the cell assembles. 

Cellular work requires getting energy by breaking energy-containing bonds in certain molecules (like ATP). 
This kind of work doesn't involve only DNA and RNA (not D). 
Energy-deficient compounds don't have energy, so they can't power cellular work (not B). 
I don't think C is the best answer because cellular work (like breaking/making bonds) can be facilitated by enzymes and other molecules made by the cell itself, not just other organisms that have a symbiotic relationship with the cell (not C).