Technician a Says Heater Hoses from the Water Pump Circulate

Technician A says heater hoses from the water pump circulate water through the heat exchanger / heater core under the dash to warm the interior of the vehicle. Technician B says the coolant should always be filled to the hot fill line on the coolant reserve reservoir. Who is correct?

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