c because a generator generates electricity with the use of another energy source like nuclear,solar,wind,fossil fuel,gasoline or in rare cases temperature 
 
        
             
        
        
        
 Gravity causes the motions of planets, stars, and galaxies. It's why the Moon orbits around the Earth, and the Earth orbits around the Sun, and the solar system orbits around the galaxy.
        
                    
             
        
        
        
Answer:
The ability of our bodies to adapt to different levels of gravity. You would become weaker and your heart is use to zero gravity. Boredom because there isn't much to in space. When intelligent people get bored, it's not pretty all the time...