Answer: The sun
Explanation: Primary producers obtain their energy via the sun through the process of photosynthesis.
 
        
             
        
        
        
Antibiotics have a tendency to weaken the immune system.
 
        
             
        
        
        
Sink to the bottom because it is more dense than the water.
        
             
        
        
        
Answer; 
C. it is the part f the atom with the greatest mass
Explanation;
The nucleus of an atom is a small dense region at the center of an atom that contains protons and neutrons. 
Almost all the mass of an atom is located in the nucleus, with a very small contribution from the electron shells.
The protons are positively charged which gives the nucleus a positive charge while the neutrons have no charge.
 
        
                    
             
        
        
        
Answer:
Nitrogenous bases known as Glutamine, Thymine, Adenine, and Cytosine.