Final answer:
As sedimentary clasts move farther from the source, they become more rounded due to the abrasion and tumbling they experience during transport. Grains also tend to become well-sorted, with similar sizes predominating at greater distances from the source rock.
Step-by-step explanation:
When considering which is true about sedimentary clasts as you move farther from the source, it is important to understand that various processes affect sediment as it is transported away from its origin. Sedimentary clasts, which are the pieces of rock or mineral that make up clastic sedimentary rock, undergo changes in size, sorting, and shape with increased transport. As clasts are moved by water, wind, or ice, the rough edges begin to wear off, leading to smooth, rounded grains. This rounding is an indicator of how far the sediment has traveled from its source.
With increasing distance from the source, grains typically become more rounded, due to the repeated tumbling and abrasion they experience during transport. Also, sediment tends to become well-sorted, meaning that the grains tend to be of a similar size because over time, the sediment is separated by the strength of the transporting medium, such as water or wind. Fine-grained sediments like silt and clay can be carried farther than large grains such as sand and gravel, which tend to settle out sooner when the current slows.
Therefore, the correct answer to the question is that as you move farther from the source, grains become more rounded. This rounding process is due to the prolonged transport and the continued weathering of grains as they collide with each other and are abraded by the transporting medium.