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.
Answer:
Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak.
Breaking bonds takes energy, forming bonds releases energy
If you break more bonds than you form it would be an endothermic reaction