After overtaking the car and the lorry, the green car wishes to continue overtaking other vehicles. Must it return to the right lane first?

A)Yes, always.
B)No, because on motorways it is not mandatory.
C)Yes, but only when vehicles are travelling behind at a higher speed.Correct
The general rule requires driving in the right lane. However, if you are going to continue overtaking, you may remain in the left lane provided you do not obstruct other vehicles approaching from behind at a higher speed. In that case, you must return to the right lane to let them pass.