The trailer air supply control (to supply air to the trailer) is typically:

Red and octagonal.. Section 6.2 (Air Brakes context): The trailer air supply is a red, octagon-shaped knob.

The trailer air supply control (to supply air to the trailer) is typically:

ANSWER BREAKDOWN
  • A. Correct. Section 6.2 (Air Brakes context): The trailer air supply is a red, octagon-shaped knob.
  • B. Incorrect. "Yellow and diamond." is not correct. Section 6.2 (Air Brakes context): The trailer air supply is a red, octagon-shaped knob.
  • C. Incorrect. "Blue and round." is not correct. Section 6.2 (Air Brakes context): The trailer air supply is a red, octagon-shaped knob.
  • D. Incorrect. "Green." is not correct. Section 6.2 (Air Brakes context): The trailer air supply is a red, octagon-shaped knob.