Which of the following methods can be used to test the trailer emergency brakes?

A) Apply the brakes while driving at a high speed and observe if the trailer stops abruptly.
B) Disconnect the trailer from the towing vehicle and manually activate the emergency brake lever on the trailer.
C) Increase the weight of the trailer and observe if the emergency brakes engage automatically.
D) Inspect the emergency brake system visually and check for any signs of damage or malfunction.