Answer:
A
Explanation:
I'm not completley sure but veins go to every location in your body while capillaries and arteries are in designated areas. 
 
        
                    
             
        
        
        
The correct answer is<span> a. Volcanic glass
Volcanic glass is also known as Obsidian. It is formed when lava cools down too rapidly and crystals grow minimally, without grains.</span>
        
             
        
        
        
Answer:
My hypothesis is that the Hawaiian Island chain was formed by a hot spot in the middle of the Pacific Plate. While the hot spot itself is fixed, the plate is moving. My data supports my hypothesis because as the plate moved over the hot spot, the islands that make up the Hawaiian Island chain were formed. 
 
        
                    
             
        
        
        
Answer:
I, II, III
Explanation:
A threshold stimulus is a stimulus that is capable to produce a response in excitable tissues such as neurons and muscle fibers. At threshold potential, the outward movement of K+ and inward movement of Na+ become equal to each other. When the potential exceeds the threshold potential, more and more Na+ enter the cell to depolarize it and to allow the opening of Na+ channels. Therefore, to fire an action potential, the threshold must be exceeded. 
Conduction of action potential is all or none phenomenon which means that either it occurs or it does not occur. As an impulse is passed by each successive part of an exon, it enters the refractory period during which there is no conduction of nerve impulse. It ensures the one-way conduction of impulse from the cell body to the axon terminal only.