Lumber shall be stacked on a level surface so that the stack is ___.

Stacking lumber on a level surface is crucial for maintaining the integrity and safety of the stack. When the stack is stable, it ensures that the weight of the lumber is evenly distributed, reducing the risk of the stack tipping over. A stable stack helps prevent accidents and injuries that could occur from falling lumber.

Being self-supporting means that the lumber can maintain its structure without additional external support. This is particularly important in construction environments where space might be limited, and materials need to be stored in a way that does not require constant monitoring. Self-supporting stacks reduce the risk of collapse, thus enhancing safety on the job site.

Since both stability and self-supporting characteristics are essential for safely stacking lumber, the best choice encompasses both aspects, making it the correct answer. This approach reinforces best practices in material handling and storage, which are critical for effective and safe electrical contracting work.