which of the following is a correct statement of the ohm's law? responses a. the resistance of a conductor is always constant. a. the resistance of a conductor is always constant. b. the current in a conductor is always proportional to the potential difference across the conductor. b. the current in a conductor is always proportional to the potential difference across the conductor. c. the resistance of a conductor increases with increasing temperature. c. the resistance of a conductor increases with increasing temperature. d. the resistance of a conductor is constant only if the temperature of the conductor is constant.