Boulders can become smaller as they are moved down a stream bed. this is an example of the process of the wearing away of rock by grinding action. explain

Erosion

Explanation:

Boulders can become smaller as they are moved down a stream bed. Sharp and angular boulders breaks down and converted into round shape pebbles which are smoother this process is called as erosion. and the eroded material of angular rocks form sand and soil in the river bed. At the end these rocks and soil at the mouth of river form delta.

im guessing the west of station b