Answer:
B. calcium has electrons in more energy levels than magnesium
Explanation:
atoms are made of three types of subatomic particles - electrons, protons and neutrons. 
Neutrons and protons reside in the nucleus of the atom and electrons reside in energy shells
electronic configuration for both Ca and Mg are as follows
Mg - 2,8,2
Ca - 2,8,8,2
outermost energy shell of Mg with electrons is the third energy level
whereas outermost energy shell of Ca with electrons is the fourth energy shell
therefore Ca has a larger atomic radius than Mg as it has one more energy shell than Mg in which electrons reside
 
        
                    
             
        
        
        
D=m/v. (Density equals mass over volume). 
So in your case density = 4.2/6 
Which equals 0.7 
Your units will be grams over milliliters 
So your answer is 0.7 g/ml
        
             
        
        
        
 <span>Therefore, the rotation of the </span>object<span> "</span>speeds<span> up" as it </span>falls. Therefore, it rotates "<span>faster" than the Earth under it, and so it </span>falls<span> slightly to the east.</span>