If an overtaking vehicle signals that it must move in, in front of you, you should

• A. Flash your lights at the overtaking vehicle.
• B. Prepare to slow down to allow room.
  Explanation:

  "An overtaking vehicle may need to move in front of you if there is traffic coming the other way. You should already be leaving enough space between you and the vehicle in front, so ensure you are and drop back to allow room if you are not."
• C. Speed up and not let the vehicle back in.