I would say energy myself, and this is because energy plays a key role in all of these. With trophic levels energy is being transferred amongst the levels. Food chain's is a map of how the energy is passed along the chain. Food web is a web of how energy is transferred, and this is why I would say energy is a keyword.
Answer:
Fungi
I hope this helped :)
A. Organic compounds - C₃N₂H₄ , C₆H₅F and C₁₂H₂₂O₁₁
Organic compounds are compounds which have Carbon except few compounds such as carbon dioxide, cyanide. Other than Carbon, other elements also present such as Hydrogen, Oxygen and Nitrogen. But Carbon is considered as the main element of organic compounds.
B. Inorganic substances - AIBr₃ , CrO₃ and <span>H</span>₂<span>O</span>₂
Inorganic substances are the compounds which do not own C-H bonds. Most inorganic compounds do not have carbon as their element except few. (Cyanides, carbon dioxide, carbon monoxide and so on are considered as inorganic although they have carbon).