How should unsupported cross-cuts on extended length cuts be supported prior to inby travel?

The requirement for using at least two rows of temporary supports on 4-foot centers prior to inby travel in unsupported cross-cuts on extended length cuts is based on safety regulations and best practices in mining operations.

This standard ensures that the integrity of the cross-cut is maintained, providing necessary support to prevent collapses or hazardous conditions that could endanger workers. By spacing the supports every 4 feet, the structure receives adequate reinforcement, distributing weight and pressure effectively, which is crucial in maintaining stability in mining environments where ground conditions may vary.

The other options suggest different spacing or insufficient arrangements that wouldn't adequately address the safety needs associated with unsupported areas. It’s essential for mine foremen to adhere to these standards to ensure a safe working environment in the mines, reflecting the importance of proper support systems in potentially unstable geological conditions.