In lieu of a shorting system, the sides or walls of an excavation or trench may be:

The correct answer highlights the standard practice for trench safety regarding the sloping of excavation walls. A slope of 3:1 means that for every 3 units of horizontal distance, the excavation wall rises by 1 unit vertically. This ratio is widely recommended since it reduces the likelihood of collapse, ensuring a more stable and safer environment for workers.

By sloping the sides at this angle, the pressure exerted by the soil is lessened compared to steeper slopes, allowing for adequate support during excavation activities. Safety regulations and best practices, including those outlined by OSHA, typically recommend a 3:1 slope in non-standard, non-engineered excavations to minimize the risk of cave-ins.

Other ratios, such as 1:3 or 2:1, suggest either a significantly steeper angle, which could pose a greater risk of collapse, or a more gradual slope that may not conform to safety guidelines. A 1:1 slope, for instance, is particularly dangerous and not typically permissible without engineering controls, as it can lead to instability in the soil. This makes the selected choice the safest and most compliant with excavation safety standards.