A brake warning lamp on the dash remains on whenever the ignition is on. If the wire to the pressure differential switch (usually a part of a combination valve or built into the master cylinder) is unplugged, the dash lamp goes out. Technician A says that this is an indication of a hydraulic brake problem. Technician B says that the problem is probably due to a stuck parking brake cable switch. Which technician is correct?

The answer is Technician A only is correct.

Explanation:

From the statement that a brake warning lamp on the dash remains usually on whenever the ignition is on, thus if the wire to the pressure differential switch (usually a part of a combination valve or built into the master cylinder) is unplugged, the dash lamp goes out. This is an indication of a hydraulic brake problem because the wire to the brake switch is disconnected thus causing no reportage. Normally, the brake warning lamp supposed to be on  usually except if faulty or wire is disconnected as described above.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me