Bone meal is an organic byproduct of the meat packing and slaughterhouse industry, composed primarily of tricalcium phosphate [$\text{Ca}_3(\text{PO}_4)_2$] and ossein collagen protein:
Raw bone meal contains approximately $3 - 4\%\ \text{N}$, $20 - 25\%\ \text{P}_2\text{O}_5$, and $25 - 30\%\ \text{CaO}$ (Calcium).
Steamed bone meal contains $1 - 2\%\ \text{N}$, $25 - 30\%\ \text{P}_2\text{O}_5$, and $30 - 33\%\ \text{CaO}$.

Humic substances (humic acid, fulvic acid, and humin) are complex, polydisperse, amorphous supramolecular associations formed during the microbial decomposition and secondary synthesis of plant and animal residues:
Spectroscopic and pyrolytic investigations (by Schnitzer, Stevenson, and Piccolo) demonstrate that humic macromolecules consist of:

• Phenolic compounds derived from lignin biodegradation.
• Quinone structures that undergo oxidative polymerization and confer redox activity.
• Abundant carboxylic acid groups ($-COOH$) providing cation exchange capacity and buffering.
• Aliphatic hydrophobic domains including fatty acids, alkanes, and lipid waxes.

In biological nitrification, the first committed step is ammonia oxidation to nitrite:

Microorganisms responsible for this conversion are Ammonia-Oxidizing Bacteria (AOB), which all carry the prefix Nitroso-, such as Nitrosomonas, Nitrosolobus, Nitrosococcus, and Nitrosospira (hence A and D are correct).
Nitrobacter performs the second step: oxidizing nitrite to nitrate ($\text{NO}_2^- \rightarrow \text{NO}_3^-$).
Thiobacillus is a sulfur-oxidizing bacterium.