Most of it follows its cycle, going back to the atmosphere. 
The image below, shows you how the nitrogen cycle is.
Hope it helped,
Happy homework/ study/ exam!
 
        
                    
             
        
        
        
A) genotype
Because the genotype means the genetic make-up of the cell, so saying that the genes of the plant are homozygous dominant show this genetic make-up of the plant. 
        
             
        
        
        
Answer:
Electron transport chain
Explanation:
Cellular respiration is the process whereby glucose is broken down in the cell to yield energy in form of ATP. This process, which is important to the metabolic functioning of every organism, occurs in three major stages namely: glycolysis, kreb's cycle and electron transport chain (ETC). 
According to this question, a stage of respiration is described as follows: 
- Two pyruvate molecules undergo a chemical reaction, combining with coenzyme A to form two acetyl-CoA molecules. 
- Two carbon dioxide molecules and two NADH molecules are formed as a result of this process.
The process depicted above is KREB'S CYCLE of cellular respiration, hence, the stage of respiration that immediately follows the process is called ELECTRON TRANSPORT CHAIN (ETC).