It means , one , only , single .. hopes this helps
        
                    
             
        
        
        
Answer:
research question: how do different humidity levels affect the heights of different types of trees 
independent variable: humidity level
dependent variable: tree height 
constants: temperature, light, duration of time 
control group: tree left outside in normal conditions
Explanation:
 
        
             
        
        
        
Answer:
birch
Explanation:
because they easily germinate hence early succession
 
        
                    
             
        
        
        
Answer:
The correct answer is B. Quadriplegia is paralysis of all four limbs.
Explanation:
Quadriplegia is a clinical sign that causes total or partial paralysis of arms and legs caused by damage to the spinal cord, specifically in some of the cervical vertebrae, or by a disease that affects motor neurons, such as the amyotrophic lateral sclerosis. In some cases, following intensive rehabilitation, some mobility can be regained.