I think option C is correct..hope it helps
        
                    
             
        
        
        
Static friction is the friction that exists between a stationary object and the surface on which it's resting.
frictional force occurs when you try to push an object alongside a surface.
        
             
        
        
        
<h3><u>Answer;</u></h3>
 the north end to the south end.
<h3><u>Explanation;</u></h3>
- Magnetic field lines from a bar magnet form lines that are closed. The direction of magnetic field is taken to be outward from the North pole of the magnet and in to the South pole of the magnet. 
- A magnetic field refers to  the area surrounding a magnet where a force is exerted on certain objects. These lines are spread out of the north end of the magnet.
- The magnetic field lines resemble a bubble.
 
        
        
        
Dipper effect of an oncoming train get louder as it approaches and sound diminishes as it goes away sound traveling