I believe it is nervous tissue
        
                    
             
        
        
        
A closed circulatory system is present in organisms with a circulating body fluid that is distinct from the fluid that directly surrounds the body's cells. 
<h3>What is the circulatory system?</h3>
The circulatory system is an organs system that works to carry out blood cells to all cells in the body.
The circulatory system is fundamental for transporting oxygen and nutrients to all cells of the body.
A closed circulatory system is a special organ system where the blood cells are not circulating in body cavities.
Learn more about closed circulatory systems here:
brainly.com/question/989029
 
        
                    
             
        
        
        
Mass is the amount of matter in any object. 
 
        
             
        
        
        
Answer:
Cells would most probably not exist because these units of life metabolize energy molecules like glucose to harness their energy for the running of biochemical processes, like active transport, to support life. However, harnessing this energy from these energy molecules is NOT 100 percent efficient. A higher percentage of energy is lost as heat in the process. 
Therefore if the cells were required to carry all molecules in and out of the cell, actively, including the energy molecules themselves (which is counterintuitive), this would require a lot of energy and would be unsustainable. This would be analogical to the counteracting and infinite loop of more fuel needed to carry the mass of the more fuel in space travel...
Learn More:
To learn more about the movement of molecules across the cell check out;
brainly.com/question/6169784
brainly.com/question/8276318
#LearnWithBrainly
 
        
             
        
        
        
Answer:
A
Explanation:
Stretching of the atrium and ventricle muscles