a. Igneous, sedimentary, metamorphic. Formed through different processes.
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Igneous Rocks: These are formed from the solidification of molten rock (magma or lava). When magma cools and crystallizes beneath the Earth's surface, it forms intrusive (or plutonic) igneous rocks, such as granite. When lava cools and solidifies on the Earth's surface, it forms extrusive (or volcanic) igneous rocks, such as basalt.
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Sedimentary Rocks: These rocks are formed through the accumulation and compaction of sediment, which can include minerals, organic matter, and fragments of other rocks. The process often involves weathering, erosion, and deposition in water, followed by lithification (the turning of sediments into solid rock). Common examples include sandstone, limestone, and shale.
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Metamorphic Rocks: These rocks are formed from existing rocks (either igneous, sedimentary, or other metamorphic rocks) that undergo a transformation due to high temperature, high pressure, and/or chemically active fluids, leading to changes in mineral composition and texture. Examples include schist, gneiss, and marble.