If a Certain Resistor Obeys Ohm's Law,its Resistance Will Change

Multiple Choice

If a certain resistor obeys Ohm's law,its resistance will change:

A) as the voltage across the resistor changes.
B) as the current through the resistor changes.
C) as the energy given off by the electrons in their collisions changes.
D) none of the above,since resistance is a constant for the given resistor.