Answer: a-Gravity
Explanation:
Soil erosion is a natural phenomena which involves the removal of the top or subsoil layers under the influence of factors such as water, wind and gravity.
According to the situation, the given activity is the mountain climbing. Generally in mountains the mass wasting is the most prominent phenomena. In mass wasting the soil, stones, debris and other materials moves downwards the slope region under the influence of gravity.
As it is shown in the figure the team mates are helping each other to climb the wall of the mountain this process is against the act of gravity. Hence, this process can be related to the soil erosion due to mass wasting against the act of gravity.
