Nitrogen.
 Plants cannot use atmospheric nitrogen directly. Nitrogen from the air must be converted into the different form so plants can absorb it. Thus plants need nitrogen-fixing bacteria to convert atmospheric nitrogen into ammonium, which is available for plants to absorb it.
 
        
             
        
        
        
B is your answer. God Bless hope this helps
 
        
                    
             
        
        
        
The answer is exposure. To simplify, the first step in the perceptual process is called exposure and refers to the method of transporting some stimulus in the closeness of a consumer so that it can be detected by one of the five human senses. In addition, the perceptual process is an order of steps that starts with stimuli in the surroundings and ends with an understanding of those stimuli. This procedure is naturally unconscious and occurs hundreds of thousands of times a day. An unconscious procedure is just one that occurs in deprived of consciousness or objective.