A neuron (also known as nerve cell) is an electrically excitable cell that takes up, processes and transmits information through electrical and chemical signals. It is one of the basic elements of the nervous system. In order that a human being can react to his environment, neurons transport stimuli.
 
        
             
        
        
        
Answer: 
The variable that does not rely on another variable. IVs can include time, weather, etc.
Explanation:
 
        
             
        
        
        
A. is your correct answer
        
             
        
        
        
Your answer would be Physical weathering because it is being caused by a physical being acting upon something