8. The diagram below shows a sedimentary rock sample.

Which agent of erosion was most likely responsible for shaping the particles forming this rock?

A) Mass movement

B) Glacial ice

C) Wind

D) Running water

Correct Answer: Option D – Running water

Erosion is the detachment of earth material from the surface. Once detached, agents like water or wind transport the material to a new location where it is deposited. The most ubiquitous form of erosion is that done by water. Running water causes erosion of soil and rocks. This is done by the friction between the constant movement of the water and the still rock or soil. Rock erodes much slower but will eventually wear away. The diagram above shows smooth surfaced pebbles, which are formed by the effect of running water.

Hence, options A, B and C are incorrect.