Amphibians are a key component of the scientific model known as because of their movement from an organism living on land and breathing air

I'm pretty sure the answer is c 

The answer is 4f======since electrostatic force is given by    we let f be the electrostatic force when  r = 1 m    if we let  denote the electrostatic force when the distance is decreased so that r = 0.5m, then    we established earlier that f = kq₁q₂. therefore    the force will now be 4f.