What materials can be placed around an ice hole to assist divers?

Using wooden pallets, burlap bags, or sand around an ice hole is beneficial for several reasons. These materials can help create a stable and safe platform for divers to prepare and enter the water. The wooden pallets provide a solid surface that can prevent slipping and falling, while burlap bags can be filled with snow or ice to help weigh down and stabilize the setup, reducing the chances of the ice hole collapsing under extra weight. Sand can be used to create barriers to control melting around the dive site or to provide additional weight to secure the setup.

In contrast, while options like sand, rocks, and gravel might seem stable, they can also be uneven or shift easily under weight. Plastic mats and ropes might not provide enough stability or support in icy environments, and the presence of nothing surrounding the ice hole leaves divers with insufficient safety measures and increases the risk of accidents. Therefore, option B is the most effective in ensuring a safe diving environment.