C. nervous system, because its triggers 
        
             
        
        
        
Answer:
Sound waves transfer energy by causing successive compressions and rarefactions in the particles of the medium without transporting the medium particles themselves. Sound in solids can also manifest as transverse waves, causing crests and troughs in the propagation medium.
 
        
             
        
        
        
Answer:
for students to do nothing
Explanation:
because doing nothing is not a course goal
 
        
             
        
        
        
Answer:
The current is   
 
Explanation:
From the question we are told that  
      The radius of the loop is  
      The  earth's magnetic field is 
       The  number of turns is  
Generally the magnetic field generated by the current in the loop is mathematically represented as 
         
Now for the earth's magnetic field to be canceled out the magnetic field generated by the loop must be equal to the magnetic field out the earth
          
=>     
      Where   is the permeability of free space with value
 is the permeability of free space with value  
        
=>     
        