Final answer:
Safety valves that are b) direct spring loaded use a spring to control the opening and closing of the valve.
Step-by-step explanation:
Safety valves can be of different types based on their design and operation. In this case, the question is asking about the type of safety valve based on the mechanism used to control the valve.
The correct option is b) direct spring loaded type. Safety valves that are direct spring loaded use a spring to control the opening and closing of the valve, ensuring the release of excessive pressure.