While Having a Discussion, Technician a Says That If the Voltmeter

While having a discussion, Technician A says that if the voltmeter reads 0.4 volt or more, the system should be flushed and refilled with new coolant to prevent corrosion of the metal parts in the system. Technician B says that the system should be flushed if the voltmeter reading is less than 0.4. Who is correct?

A) A only
B) B only
C) Both A and B
D) Neither A nor B