Answer:A. differing densities of the elements that make up the Earth. 
Explanation: The densities of the different materials making up the Earth surface and the Earth crust, due to the varying density of these materials it makes it difficult to break certain types of materials.
When the time required to break down materials differ,the earth's surface will have different layers caused by the time difference between the breakdown of these materials.
The more the density of the material the more difficult it is to break it down.
 
        
             
        
        
        
A volcanic island arc is formed when :
A. Two oceanic plates coverage and form an subduction zone.
Hope this helps :)
        
                    
             
        
        
        
That statement is true
Brain drain phenomenon happened when talented and educated individuals decided to migrate into another country in search of new career opportunities.
since they're searching for new career opportunities, Small Island and unstable nations are the least likely destination for their journey.
        
                    
             
        
        
        
Answer:
Because most Albanians earn less than $100 a month
Explanation: Italian and Greek manufacturers have built factories in Albania in order to take advantage of the low wages.