The correct answer is (a). The Dravidian Rock System is a group of sedimentary and igneous rocks that formed during the Silurian period. The rocks are found in the southern and western parts of India, and they are important for the study of the Earth’s history.
The Dravidian Rock System is made up of a variety of different types of rocks, including sandstone, shale, limestone, and granite. The rocks were formed by the deposition of sediments in shallow seas, and they were later intruded by igneous rocks. The rocks are important for the study of the Earth’s history because they provide evidence of the changes that have taken place on the planet over time.
The other options are incorrect because they are not related to the Silurian period. The Purana Rock System is a group of sedimentary rocks that formed during the Paleozoic era, the Aryan Rock System is a group of igneous rocks that formed during the Mesozoic era, and the Archaean Rock System is a group of igneous rocks that formed during the Precambrian era.