Final answer:
The process described is erosion (B), which causes rocks to gradually lose their sharp edges and corners, resulting in a more spherical shape over time as the protruding parts of the rock face more weathering.
Step-by-step explanation:
Processes Leading to Rounded Rock Shapes
When water enters joints in the rock, it weathers the material, especially the corners and edges, smoothing them into a more rounded shape. This process happens because these protruding parts of the rock face more weathering and erosion due to increased surface area exposed to the elements such as water, wind, and temperature changes. Over time, these forces can erode the sharp edges and corners, leading to a spherical shape of the rock. This is not an example of sedimentation, spherulitic weathering, or volcanic activity, nor is it typically associated with the transporting of fragments, which describes erosion more generally.
According to what's described in the student's question, the correct answer would be B) Erosion. Erosion, in this context, refers to the grinding down and smoothing of the rock by weathering agents such as water. As water seeps into cracks and freezes, the expansion can cause pieces of the rock to break off. Over time, the continued action of water can round the rock through a process of mechanical weathering, which is different from chemical weathering where the composition of the rock itself is altered.