Final answer:
None of the provided options represent a safe method for working on a fragile roof. Instead, using crawl boards, roof ladders, fall arrest harnesses, and ensuring dry conditions are crucial safety measures that should be followed.
Step-by-step explanation:
What is a safe method of working on a fragile roof? Working on a fragile roof requires strict adherence to safety measures to prevent accidents and injuries. The safe options provided do not include stepping only on the roof's central area or using rigid ladders for access. In contrast, it is imperative to avoid working during wet weather, as it can increase the risk of slips and falls. Wearing safety harnesses is critical and should never be avoided. Thus, options (a), (b), and (d) represent unsafe practices and are incorrect. Safety harnesses provide a key method of fall protection, making option (d) particularly unsafe. Therefore, none of the given options are considered safe ways to work on a fragile roof.
A more comprehensive safety approach for working on fragile roofs includes employing crawl boards or roof ladders, using fall arrest harnesses, ensuring that ladders are properly secured, and working in dry conditions to minimize slipping risks. These measures can greatly reduce the dangers associated with working on fragile roofing materials.