ALL OF THE ABOVE! All include human activity
        
             
        
        
        
Answer:
Valkyries take the souls of people who died bravely in battle to valhalla
Explanation:
I am a mythology nerd 
 
        
                    
             
        
        
        
They add different things to the car so that they can make the cars faster so they can go onto the market they also make the car more expensive so they can make more money. Don't know if that helps but there.