Oxygen is needed by aerobic organisms for cellular respiration process. Oxygen happens when the muscles are working faster than energy can be produced. Energy is still produced but anaerobic process is done to cope up. The signs of oxygen debt are panting and muscle fatigue. 
        
             
        
        
        
Answer:
CO₂
Explanation:
In chemistry we use subscripts after the element represented by that amount. 
 
        
                    
             
        
        
        
The top of the Stigma is sticky and is where the pollen attaches to it. 
I hope this is what you wanted 
        
             
        
        
        
I think the answer would be A , break the darkness period with a flash of light for some time so that the plants can bloom all year round.
        
                    
             
        
        
        
I do not know at ALL. =( Sorry.