Correct Option
The correct option is (c) 2 and 3 only.
Explanation
Rocks are classified into three major groups based on their mode of formation: Igneous, Sedimentary, and Metamorphic. Sedimentary rocks are formed by the accumulation, compaction, and cementation (lithification) of sediments derived from older rocks or organic remains over long periods.
Statement-wise Analysis
- Statement 1 is Incorrect. Rocks formed by the cooling and solidification of molten magma are known as Igneous Rocks (e.g., Granite, Basalt). Sedimentary rocks are formed through the deposition and lithification of rock fragments, minerals, or organic matter, not by the cooling of magma.
- Statement 2 is Correct. Sedimentary rocks are formed at relatively low temperatures and pressures on the Earth's surface. As sediments accumulate in layers, the remains of plants, animals, and microorganisms often get trapped and preserved between these layers. Therefore, fossils are a distinct characteristic of sedimentary rocks.
- Statement 3 is Correct. Sandstone is a classic example of a mechanically formed (clastic) sedimentary rock. It is created by the cementation of sand grains (quartz fragments) accumulated over time.
Key Takeaway
Sedimentary rocks are characterized by stratification (layering) and the presence of fossils, whereas Igneous rocks are crystalline and formed from cooling magma, devoid of fossils.