Answer:
earth strong gravity 
Explanation:
 The only planet that have water bodies is earth. We know that water is one of the important factors for all living organism. Liquid water exists on the earth's surface is due to the atmospheric pressure. The reason behind this is not completely mentioned. 
There are so many hypothesis about it. Out of given options the correct option is earth's strong gravity.
Hence, the correct option is (b) " earth strong gravity ".
 
        
                    
             
        
        
        
Answer:
This is because motion is intended to occur but at zero acceleration. It means at a constant velocity, henceFor that to happen the pulling force F must exactly equal the frictional force Fk . 
 
        
             
        
        
        
 The answer is c, but I'm not sure, just so you know