Answer:
Rigel 
hope it is helpful to you
 
        
             
        
        
        
Based on the above sources, the most economical to use is the hydroelectric, since there is a fast-moving current in the river. Also, it is the commonly used energy-generation process. For wind turbine, it would require a minimum of 8kph to power the wind turbine, in this case is not sufficient. Coal deposit is not likely an option because this has some environmental concerns. Solar is not also an option since the village frequently has rainy days.
        
                    
             
        
        
        
B. Langerhans cells transport harmful substances to white blood cells.
I think this is the correct answer, Good Luck!