Respiratory and circulatory systems work hand in hand to expel wastes. respiratory system removes CO2 and the circulatory uses the blood as a medium to move excess salts and water from source to sink. 
        
             
        
        
        

They are further classified into: fish, amphibians, birds, reptiles and mammals.
I hope I've helped : )
 
        
                    
             
        
        
        
Answer:
Archaea
Explanation:
Archaea is another term for Archaebacteria. also known as Bacteria which fits all the traits from the question.
 
        
             
        
        
        
Answer:
 it gets lower
Explanation:
when milk begins to ferment it gets sour becoming more acidic and the pH gets lower.
 
        
             
        
        
        
Answer:
True.
Explanation:
Antigen may be defined as the chemical that has the ability to evoke the  and immune response and can harm the living organisms. The specific antibody are produced against the immune response.
The antigens has evolved different mechanisms to prevent themselves from them the immune system of the host. The antigenic shift is the most common change that might occur in viruses that helps the antigen to protect itself by changing its genetic material. No anti viral drugs are available for the viruses.
Thus, the answer is true.