The correct answer is (d), quartz. Quartz is an anisotropic material, which means that its properties vary depending on the direction in which they are measured. For example, the speed of sound in quartz is different in the direction parallel to the crystal axes than in the direction perpendicular to the crystal axes. This anisotropy is due to the crystal structure of quartz, which is made up of silicon and oxygen atoms arranged in a tetrahedral arrangement. The tetrahedra are linked together to form a three-dimensional network, and the direction of the tetrahedral axes determines the direction of the crystal axes.
Glass, rubber, and plastic are all isotropic materials, which means that their properties are the same in all directions. This is because these materials are not made up of crystals, but rather of randomly arranged molecules.
In conclusion, the correct answer to the question “Which one of the following is anisotropic in nature?” is (d), quartz.