Final answer:
The parts of a machine that need to be guarded include fan blades, abrasive wheel machinery, revolving barrels, containers, and drums, as well as power transmission apparatus to protect against hazards such as entanglement and flying debris. Correct answer is all of the provided options (a, b, c, and d).
Step-by-step explanation:
The parts of a machine that must be guarded to ensure safety are a. Fan Blades, b. Abrasive Wheel Machinery, c. Revolving Barrels, Containers, and Drums, and d. Power Transmission Apparatus. These components can pose significant hazards such as pinch points, flying debris, or entanglement that can lead to severe injuries or fatalities.
Guards are implemented on machines to prevent direct contact with moving parts and protect workers from the associated risks. All of the provided options (a, b, c, and d) are parts of a machine that should be guarded to ensure a safe working environment and minimize the potential for accidents and injuries.