Answer:
b) from a region of high pressure to a region of low pressure
Explanation:
Blood flow is measured in blood volume per unit time. It is the movement of blood through an organ, tissue or vessel. It is initiated when ventricles in heart contract leading to its ejection at high pressure. Major arteries receive this blood and they further transport it at high pressure to smaller arteries, arterioles and capillaries. Hence arteries have thick walls to withstand this pressure. The pressure decreases when blood reaches to veins hence their walls are not that thick.  Hence, blood flows from a region of high pressure to a region of low pressure.
 
        
             
        
        
        
Answer:
Viruses mutate very quickly The major reason that viruses evolve faster than say, mosquitoes or snakes or bed bugs, is because they multiply faster than other organisms. And that means every new individual is an opportunity for new mutations as they make a copy of their genetic material. Many of those mutations have no noticeable effect.
Explanation:
 
        
             
        
        
        
Answer:
Animals making the territory with example Lion, Tiger, hyena among others
Explanation:
Animals marks their territory through secretion of pheromones, some makes sound, it is a form of behavioral act that allows to protect ones territory or boundary
 
        
             
        
        
        
An atom that gains a negative electron, it becomes a negative ion. If it loses an electron it becomes a positive ion. Some atoms lose electrons and become positive ions. Others gain electrons and become negative ions.
 
        
                    
             
        
        
        
it only need one to fertilize a egg in a flower