The formation of sedimentary rocks typically begins with:

• A. Burial and compaction of sediments
• B. Solidification of magma
• C. Metamorphism due to pressure
• D. Crystal growth from lava

Answer: (A)

Sedimentary rocks form when loose sediment produced by weathering is turned into rock through lithification. The key idea is that with burial, the overlying layers press down on the lower sediments, squeezing out air and water. This compaction reduces pore space and, as minerals dissolved in water precipitate, they cement the grains together. That combination of burial, compaction, and cementation converts loose sediment into solid rock.

The other options describe processes that create different rock types. Solidification of magma produces igneous rocks; metamorphism occurs when rocks are transformed by high pressure and temperature; crystal growth from lava is part of forming igneous rocks as well.