Final answer:
The longer sediment is transported, the smaller and more sorted the grains become. This means the grain size decreases and sorting increases, indicating a history of extended transport before lithification.
Step-by-step explanation:
The grain size and sorting of sedimentary rocks can tell us a lot about the history of the sediment that formed them. The longer sediment has been transported before it is deposited and lithified into sedimentary rock, the more alterations you can expect to observe in its grain size and sorting. As sediments travel, the particles encounter friction and impact with other particles, which tends to break them down and wear away the edges, causing the grain size to decrease. At the same time, the sorting increases, because sediment transportation mechanisms like water and wind tend to sort particles due to differences in their size, shape, and density. The longer the transportation phase, the more uniform in size and better sorted the particles tend to be.
Therefore, the correct answer to the student's question is that the longer sediment has been transported before it is deposited and lithified into a sedimentary rock, the grain size decreases and the sorting increases (option 2). This is because during transport, smaller grains are produced from larger ones through abrasion and sorting mechanisms tend to separate grains by size, leading to a sediment that is well-sorted and has smaller grain size.