Final answer:
When debris and soil fall down a steep hill, the type of mass movement described is a mudflow, particularly following heavy rainfall resulting in saturated slope material.
Step-by-step explanation:
After a heavy rainfall, debris and soil falling down a steep hill would be described as a mudflow. A mudflow is a type of mass movement where a slurry of rock and mud, which has become saturated with water, moves down a slope. This can occur after periods of intense rainfall, which can lead to the saturation of slope material. Other types of mass movement include landslides, which can involve more dry materials, and creep, which is a slower process usually impacting soil.
The correct answer to the question of what type of mass movement is described when debris and soil fall down a steep hill days after heavy rainfall is c. Mudflow.