Answer:
B) Nitrogen-fixing bacteria and lightning
Explanation:
Nitrogen cycle is the natural process in which atmospheric nitrogen is converted into nitrite and nitrate with the help of bacteria.
Nitrogen cycle is directly dependent on nitrogen-fixing bacteria and lightning. 
As bacteria are responsible for most of the chemical conversion in the nitrogen cycle such as nitrogen fixation (first step) is done by soil bacteria (Cyanobacteria) that form ammonia, which is toxic to plants; nitrification in which ammonia is converted into nitrites and nitrates with the help of Nitrobacter and denitrification bacteria involve Pseudomonas, and Achromobacter which convert nitrite and nitrate into nitrogen.
The lightning breaks nitrogen molecules and allow  it to combine with oxygen in atmosphere which further dissolve in rain and form nitrates.
Hence, the nitrogen cycle is most directly dependent upon nitrogen-fixing bacteria and lightning and the correct option is B.
 
        
             
        
        
        
Answer: corals, crabs, oysters and urchins 
Explanation:
 
        
                    
             
        
        
        
I think it may be this but not quite sure
Lipids are primarily hydrophobic in nature, but there are a large variety of lipids such as fatty acids, mono-, di-, and triglycerides, for example (check wikipedia for more examples). 
<span>Proteins are polymers of amino acids. </span>
<span>Nucleic acids are polymers of nucleotides.</span>