All living things need energy; it is a requirement for life. In a typical cell, ATP, the high energy molecule, is produced in the MITOCHONDRIA <span>in the presence of a sugar (glucose) and OXYGEN.
Answers are in the cap. letters!
Hope this helps!</span>
        
                    
             
        
        
        
C. They are not enclosed by a membrane. 
D is incorrect because Ribosomes do not contain DNA, the nucleolus does.
B is also incorrect because they aren't located outside the cell, they're in the cell, on the endoplasmic reticulum.
Hoped this helped :)
        
                    
             
        
        
        
Answer:
Marine ecosystem have biotic organisms like phytoplankton and photosynthetic algae that do photosynthesis and converts the atmospheric carbon dioxide into organic matter most of the carbon dioxide is released when other organisms eat phytoplankton and release the carbon dioxide through respiration.
But some of the algae and phytoplanktons die naturally get down to the bottom of the ocean where they make carbon sink. Some organisms accumulate CO₂ in their exoskeleton that is made up of calcium carbonate.  
Therefore this use of carbon by living organisms in oceans brings carbon dioxide from the atmosphere to oceans. This is why the ocean plays a critical role in the carbon cycle and called carbon sink.
 
        
             
        
        
        
Sweat, mucus, tears, and saliva all contain enzymes that kill pathogens.