Which one of the following statements is not correct in connection with electrodynamic instruments?

A. As the coils are air-cored, these instruments are free from hysteresis and eddy current losses

B. These instruments have a high torque/weight ratio and hence have a high sensitivity

C. These instruments can be used on both a.c. and d.c. and are very useful where accurate r.m.s. values of voltage irrespective of waveforms, are required

D. These are more expensive than either PMMC or moving-iron type instruments

Answer: Option B