Hello there :)
What I could say though are the following of the function of proteins:
Building Tissues and Muscles. Protein is necessary in building and repairing body tissues. ...
Hormone Production. ...
Enzymes. ...
Immune Function. ...
Energy.
Well, first off the spongy mesophyll does have some chloroplasts, however they are located quite far from the surface of the leaf where most of the chloroplasts are. Therefore they don't get much light and don't contribute a lot to photosynthesis in the leaf. So why should the leaf waste the energy in making chloroplasts if there is not enough light to make them all efficient enough at photosynthesis?
I would say (C) considering all of the others seem positive
Hope this was helpful!! :)