D. Watershed - a watershed is the area in which runoff, rivers, and streams run into a larger body of water
        
                    
             
        
        
        
Answer:
The three parts of an amino acid are the carboxyl group, the amino group, and the central carbon that contains the R group.
Explanation:
 
        
             
        
        
        
<u>Answer;</u>
C) organic matter; rocks. 
The uppermost horizon, horizon O, in this profile is composed mostly of <u>organic matter</u>, while the lower horizon, horizon C, is composed mostly of <u>rocks.</u>
<u>Explanation;</u>
-Soil contains the following major horizons, that is A B and C. Some soils may have horizon O, which may be thin or thick or even lack in some soils. This O horizon is found at the surface of many soils and normally contains organic materials at various decomposition stages. these are materials such as plants, leaves and bugs.
 -C horizon is the layer that is below the B horizon. It contains larger weathered fragments or broken up-bedrock.
 
        
                    
             
        
        
        
blood flows at a high pressure, so if the arteries are thin and less muscular, the arteries can explode due to the pressure. so it needs thick and muscular properties so that it can withstand the increasing pressure of the flow of blood.
im not sure why it needs to be elastic. Hope it helped :)