In an electrical circuit R, L, C and an a.c. voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage the current in the circuit is\[\pi /3\]. If instead, C is removed from the circuit, the phase difference is again \[\pi /3\]. The power factor of the circuit is :

• A. \[1/2\]
• B. \[1/\sqrt{2}\]
• C. 1 
• D. \[\sqrt{3}/2\]