The correct answer is D) DC voltmeter. In a DC voltmeter, an internal resistance is placed in series with the meter movement in order to limit the current flowing through the meter and protect it from damage. This internal resistance, known as a multiplier resistor, ensures that the voltmeter displays the correct voltage reading by creating a voltage drop proportional to the input voltage. The other options are incorrect because: - AC frequency meters and AC ammeters do not use internal resistors in series with the meter movement. - DC ammeters are designed to measure current, not voltage, and therefore do not require an internal series resistor.