Answer:
Technician B
Step-by-step explanation:
A thermostat being stuck in an open position allows coolant to constantly circulate through the radiator which will cause a drop in the temperature of the engine. Hence, thermostat being stuck in an open position has nothing to do with burst upper radiator.
On the other hand, a radiator cap controls the pressure within the radiator which needs to be kept constant in order prevent overheating or damage to the radiator itself.
Therefore, technician B is correct.