Phasor diagram of load voltage (V), current in pressure coil $$(I_p)$$ and current in current coil $$(I_C)$$ is shown in the figure when an electrodynamic watt meter is used to measure power. The reading of the watt meter will be proportional to

A

$$ \cos (\beta + \psi) $$

B

$$ \cos \psi $$

C

$$ \cos \beta \cos \psi) $$

D

$$ \cos \beta \cos (\beta + \psi) $$