What type of rock formations are in the sedimentary group?

• A. Limestone, sandstone, shale, and conglomerate
• B. Granite, basalt, diorite, and gabbro
• C. Quartz, feldspar, mica, and olivine
• D. Marble, dolostone, chalk, and chert

Answer: (A)

Rocks are grouped by how they form, and sedimentary rocks come from particles that settle out of water or air and become compacted and cemented over time. The best choice lists limestone, sandstone, shale, and conglomerate, which are classic sedimentary rocks formed by deposition and lithification in environments like oceans, rivers, and deserts. Limestone forms from accumulated carbonate material, sandstone from sand-sized grains, shale from fine clay that compacts into thin layers, and conglomerate from larger rounded grains cemented together. This set exemplifies the sedimentary group, unlike igneous rocks such as granite and basalt that crystallize from molten rock, or rocks like marble that are metamorphic.