Which of the following is used to churn up flat arena footing?

The use of a rototiller is highly effective for churning up flat arena footing because it is specifically designed to mix and aerate soil or footing material. A rototiller features rotating blades that break up compacted surfaces and ensure they are well-mixed, which is crucial for maintaining optimal footing conditions in equestrian arenas. This ensures a softer, more even surface that provides good traction for horses and reduces the risk of injury during exercises or competitions.

When considering the other options, they either do not provide the same level of soil aeration and mixing or are designed for different purposes. A shovel is primarily used for digging or moving materials, which would not effectively churn footing. A rake is generally used for leveling or spreading materials rather than deeply mixing them. While a harrow is designed for breaking up and aerating the soil, it may not be as effective for flat arena footing as a rototiller, particularly in managing specific materials used in equestrian arenas. Thus, the rototiller stands out as the most suitable tool for this specific task.