The correct answer is: a) Igneous rocks.
Igneous rocks are formed when magma or lava cools and solidifies. The minerals in igneous rocks are typically red or reddish-brown in color, which gives red soils their characteristic color.
Sedimentary rocks are formed when sediments, such as sand, silt, and clay, are deposited and compacted over time. Sedimentary rocks can be any color, but they are not typically red.
Metamorphic rocks are formed when existing rocks are subjected to heat and pressure. Metamorphic rocks can be any color, but they are not typically red.
Volcanic rocks are formed when magma or lava erupts from a volcano. Volcanic rocks can be any color, but they are not typically red.
In addition to their characteristic color, red soils are also typically rich in iron and aluminum. These minerals give red soils their ability to retain water and nutrients, which makes them ideal for agriculture.