A vehicle driver extends their arm horizontally with the palm of the hand facing backwards — what does this indicate?

A vehicle driver extends their arm horizontally with the palm of the hand facing backwards — what does this indicate?
A)That they are going to turn left.
B)That they intend to bring the vehicle to a stop or considerably slow its movement.
C)That they are going to reverse.Correct
If no reversing light is available, this shall be signalled with the left arm extended and the palm of the hand facing backwards.