What is a common indicator that an excavator is on an unsafe slope?

The correct choice highlights a critical safety concern when operating an excavator on a slope. If an excavator begins to slide or roll, it is a clear and immediate sign that the machine is not secure on the slope. This movement indicates that the weight distribution is not stable, which could lead to a loss of control and potential tipping.

It is important to recognize that excavators have specific center of gravity and stability limits. When working on inclines or uneven terrain, operators must constantly monitor their equipment's position. The occurrence of sliding or rolling often suggests that the ground may not be sufficiently compacted, the slope is too steep, or the excavator is improperly loaded. Addressing these issues is crucial for safety.

In contrast, the other options do not provide reliable indicators of safety. A smoothly moving machine or a balanced operator can occur on slopes that still have potential risks, while a lack of noise from the engine is not a direct reflection of stability but could merely indicate operational conditions that are unrelated to the slope safety. Understanding these distinctions is important for safe excavator operation.