Answer:
The answer is A
By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.
 
        
                    
             
        
        
        
I've learned that the circulatory system is responsible for transporting nutrients and blood throughout the entire body :D
        
             
        
        
        
Synergistic Interaction 
Hope helps uh :)
        
             
        
        
        
Answer:
James Watson and Francis Crick were the first to discover the structure of DNA in the 1950s