The correct answer is compaction and cementation.
With the build-up of the layers of sediments, the pressure on the lower layers enhances. The layers are clasped together and any water mixed in sediments is eliminated out. This procedure is known as compaction.
At the similar time, the particles of the sediment start to conglomerate with each other, and they are cemented together either by minerals or by clay like calcite or silica. After the procedure of cementation and compaction, the sequence of sedimentary has modified into a sedimentary rock.