Reactants. Reactants are the substances that are needed for a chemical reaction to occur. Without reactants there are no products.
        
                    
             
        
        
        
Fossils are found of giraffes with short necks.
Lamarck believed the giraffes stretched their necks and passed it to their offspring
necks grew longer due to stretching.
giraffes need long necks for food and evolution provided it to them
        
             
        
        
        
The
zebrafish lineage is the studied gene who evolved most rapidly as shown in its
branch where it manifest to have the longest lineages.<span> The changing branch lengths indicates
that the gene has evolved at different rates in each lineages and the branch length
is proportional to amount of the genetic variation in each linear.</span>
 
        
                    
             
        
        
        
The answer is option B "psychiatrist."  Psychiatrist are specialized in medicine and on finding cures for common diseases which would make them doctors. Also its not option A because a <span> psychologist is a person who studies in behaviors which is a therapist, its not option C because a social worker works mainly in families but not for the health. Its also not option D because a case manager who is placed to render court cases.
Hope this helps!</span>