Question

which parts of a machine must be guarded? fan blades abrasive wheel machinery revolving barrels, containers, and drums power transmission apparatus submit

Explanation:

All of these parts (Fan Blades, Abrasive Wheel Machinery, Revolving Barrels, Containers, and Drums, Power Transmission Apparatus) pose significant safety hazards. Fan blades can cause severe injury if contacted. Abrasive wheel machinery can shatter or throw debris. Revolving barrels/containers/drums can trap body parts. Power transmission apparatus (like belts, gears) can cause entanglement.

Answer:

All options (Fan Blades, Abrasive Wheel Machinery, Revolving Barrels, Containers, and Drums, Power Transmission Apparatus) should be guarded.