Which statement best defines sedimentary rock?

Which statement best defines sedimentary rock?

• A. Rock that forms when sediments are compacted and cemented together
• B. Rock formed by the solidification of molten magma
• C. Rock changed in structure by heat, moisture, and pressure
• D. Rock formed by precipitation from mineral-rich solutions

Answer: (A)

Sedimentary rocks form when loose sediments settle in layers and are turned into solid rock through lithification, which is mainly compaction and cementation. The sediments—pieces of previously existing rocks, minerals, or organic material—accumulate in environments like rivers, lakes, or oceans, and over time the weight from overlying layers squeezes them together (compaction). Minerals dissolved in water flow between the grains and crystallize, binding the particles into a solid rock (cementation). This process captures the essence of sedimentary rocks as rocks formed from deposited material that has been consolidated.

The other descriptions point to different rock types or specific sedimentary processes: rock formed from cooling magma is igneous; rock altered by heat and pressure is metamorphic; rock formed by precipitation from mineral-rich solutions describes chemical sedimentary rocks, which are still sedimentary but represent a more specific pathway within the broader category.