A multiple lift is considered critical when it entails:

A multiple lift is considered critical when it involves more than one hoist on the same load handling equipment because this situation heightens the complexity and risks associated with the lift operation. When multiple hoists are used, coordination is required to ensure that the load is lifted evenly and safely, which reduces the risk of tipping, swinging, or dropping the load.

Additionally, using multiple hoists introduces challenges such as ensuring that each hoist is correctly calibrated and that the load is balanced among the hoists. This requires detailed planning and communication among the personnel involved in the lift. The potential for mechanical failure with more components in use adds to the critical nature of such lifts, necessitating rigorous safety measures and protocols to mitigate these risks.

In the context of the other choices, while involving multiple personnel is important for safety and coordination, it does not inherently make a lift critical in the same way that multiple hoists do. A single hoist is simply a common lifting approach, and lifting items below ground level carries its own considerations, but these are not necessarily indicative of a critical lift scenario in the context of using multiple hoists.