The underlying geological structure of Bihar is predominantly:

Igneous rocks
Metamorphic rocks
Sedimentary rocks
Volcanic rocks

The correct answer is: c) Sedimentary rocks.

Sedimentary rocks are the most common type of rock on Earth’s surface. They are formed when pieces of other rocks, minerals, or organic matter are transported by water, wind, or ice and then deposited in layers. Over time, these layers are compacted and cemented together to form sedimentary rocks.

The underlying geological structure of Bihar is predominantly sedimentary rocks. These rocks were formed from the deposition of sediments from the Himalayas and the Ganges River. The sediments were deposited in a series of basins, which were then uplifted and folded to form the present-day topography of Bihar.

Igneous rocks are formed when magma or lava cools and solidifies. Magma is molten rock that is found beneath the Earth’s surface. Lava is magma that has reached the Earth’s surface. Igneous rocks can be classified into two types: intrusive and extrusive. Intrusive igneous rocks are formed when magma cools and solidifies beneath the Earth’s surface. Extrusive igneous rocks are formed when lava cools and solidifies on the Earth’s surface.

Metamorphic rocks are formed when existing rocks are subjected to heat and pressure. The heat and pressure can cause the rocks to change their shape, texture, and composition. Metamorphic rocks can be classified into two types: foliated and non-foliated. Foliated metamorphic rocks have a layered appearance, which is caused by the alignment of minerals in the rock. Non-foliated metamorphic rocks do not have a layered appearance.

Volcanic rocks are formed when magma or lava erupts from a volcano. Magma is molten rock that is found beneath the Earth’s surface. Lava is magma that has reached the Earth’s surface. Volcanic rocks can be classified into two types: extrusive and intrusive. Extrusive volcanic rocks are formed when lava cools and solidifies on the Earth’s surface. Intrusive volcanic rocks are formed when magma cools and solidifies beneath the Earth’s surface.