Which one of the following statements regarding the permanent magnet moving coil instruments is NOT true?

• A. The relationship between coil current and deflection is not governed by the pole shape of the magnet
• B. The instruments can measure the sum of two currents using two co-planar coils
• C. The instruments can measure the ratio of two currents using two crossed coils
• D. The instruments cannot measure the rms values of ac currents