Which statement best describes how sedimentary rocks form?

• A. Formed by cooling magma
• B. Formed by metamorphism
• C. Formed by precipitation from molten rock
• D. Formed by the compaction and cementation of sediments

Answer: (D)

Sedimentary rocks form when loose sediments are deposited, buried, and turned into rock through lithification, which happens mainly by compaction and cementation. As layers build up, the weight compresses the grains, squeezing out water and reducing pore space (compaction). Minerals dissolved in groundwater precipitate between the grains, binding them together (cementation). This process creates solid rock like sandstone or limestone from accumulated fragments or chemical/biogenic precipitates. The other options describe different rock-forming processes: igneous rocks come from cooling magma, metamorphic rocks from heat and pressure altering existing rocks, and precipitation from molten material isn’t a standard formation path.