Answer:
C. Protein
Explanation:
Proteins contain C, H, O, and N.
Most notably, they contain an R group (aka a side chain), which is different for each for amino acid. The R group is symbolized by the letter R in the image.
In addition to binding actin, the myosin heads bind and hydrolyze ATP, which provides the energy to drive filament sliding. This translation of chemical energy to movement is mediated by changes in the shape of myosin resulting from ATP binding.
