The correct answer is D. 4.6 kg/cm2.
The brake pipe (BP) is a system of pipes that supplies compressed air to the brakes on a train. The BP is pressurized by the train’s air compressor, and the pressure in the BP is regulated by a brake valve. The brake valve is operated by the train’s driver, and it controls the flow of air to the brakes.
The BP pressure in the guard cab of an EMU shall be 4.6 kg/cm2. This is the minimum pressure required to ensure that the brakes on the train will operate effectively. The BP pressure in the motorman’s cab shall also be 4.6 kg/cm2. This is to ensure that the motorman is able to control the train’s brakes effectively.
The other options are incorrect because they are not the minimum required BP for the guard cab of an EMU.