Final answer:
Yes, valves can be placed between a boiler and a water column if they are locked or sealed open to prevent accidental closure and ensure safety.
Step-by-step explanation:
The question asks whether valves can be placed between a boiler and a water column. The correct answer is a) Yes, if they are locked or sealed open. The reasoning behind this is that such valves would need to remain open to ensure consistent communication between the boiler and the water column for accurate water level readings. If valves were to be accidentally closed, it could compromise the system's safety. As such, valves should either be locked or sealed open to prevent accidental closure. This is particularly important in steam systems to prevent incidents that may arise from incorrect water level measurements such as overheating or boiler explosion.