40. In the igneous rock chart, igneous rocks are classified primarily on the basis of a hardness b. texture and mineralogy c. mode of occurrence d. none of these

The correct option is: b. texture and mineralogy

Explanation:

Igneous rocks, also known as the magmatic rocks, is one of three main types of rocks that is formed by the solidification of magma, with or without the process of crystallization. These rocks are mainly found in the oceanic crust, basins, land surface and shields.

The igneous rocks are primarily classified on the basis of texture and composition or mineralogy.

c. mode of occurrence

Explanation:

Igneous rocks -

The three main types of rock are the - metamorphic, sedimentary and igneous rocks.

The formation of the Igneous rocks are via cooling and solidification of the lava or magma.

The igneous rock are classified on the basics of the mode of occurrence as follow -

1. Volcanic

2. Plutonic

3. Hypabyssal.