Answer: Gas exchange that occurs at the level of the tissues is called internal respiration. The correct option is C.
Explanation:
Respiration a process in living organisms involves the production of energy, with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances. There are about four types of respiration and these includes:
- Ventilation
- External respiration
- Internal respiration 
- cellular respiration
 In respiration, passive movement of gases by diffusion occurs between cell surfaces in a process called gas exchange. Without this process, oxygen cannot be taken into the cells and carbondioxide released. I hope this helps. Thanks.
 
        
                    
             
        
        
        
Answer:
c. a trait with four alleles
Explanation:
 
        
                    
             
        
        
        
Hi there! 
The answer would be D, that ants count their steps whole walking, because the amount of steps are either longer or shorter depending on whether the ant has stilts or not, and this is caused by the ants counting their steps. 
Hope this helps!
        
                    
             
        
        
        
Centeral nervous system includes the brain and spinal cord while the peripheral includes nerves that branch out
        
                    
             
        
        
        
Answer:
Matter in an ecosystem: 
- must be continuously replenished
- is recycled and reused
-  is returned to the earth by decomposers