The correct answer is: B. approximately 0°
The two pressure coils in a single phase power factor meter are connected in series with the load. The current in the pressure coils is therefore in phase with the voltage across the load. The phase difference between the currents in the two pressure coils is therefore approximately 0°.
Option A is incorrect because the phase difference between the currents in the two pressure coils is not exactly 0°. Option C is incorrect because the phase difference between the currents in the two pressure coils is not exactly 90°. Option D is incorrect because the phase difference between the currents in the two pressure coils is not approximately 90°.