These four satellites are often called the Galilean moons to honor the Italian astronomer Galileo
        
                    
             
        
        
        
Answer:
D. A segment of DNA molecule
Explanation:
Gene is a segment of a DNA molecule that holds instruction needed for the synthesis of useful products (protein). Ideally, DNA is the storage material of genetic information in a cell. The DNA harbors the GENE, which itself is being expressed in order to use the information contained in it to produce useful products responsible for the phenotype of an organism.
A gene contains sequences made up of nucleotide bases that determines the sequence of amino acids to be produced, and ultimately the type of protein. 
 
        
                    
             
        
        
        
Since viruses are nonliving, they will need a host in order to take over and spread. Thus, viruses need help in order to reproduce. However on the other hand, Prions are also NON-living but they do not reproduce, they are protein that are not folded properly and continue to create those badly folded proteins to alter the cell.
        
             
        
        
        
Answer:
4v/f
Explanation:
wavelength = wave velocity/frequency