Chemistry · States of Matter - Gases, Liquids and Solids

The correct option is C.

Amorphous solids are isotropic. That is, they exhibit uniform properties in all directions. The thermal and electrical conductivities, coefficient of thermal expansion, and refractive index of an amorphous solid have the same value in whatever direction the properties are measured.

This option is incorrect because Ionic solids are composed of cations and anions held together by electrostatic forces. Due to the strength of these interactions, ionic solids tend to be hard, brittle, and have high melting points.

This option is incorrect because Molecular solids are composed of discrete molecules held together by intermolecular forces. Because these interactions are relatively weak, molecular solids tend to be soft and have low to moderate melting points.

This option is correct because Amorphous solids are isotropic. That is, they exhibit uniform properties in all directions. 

This option is incorrect because Metallic solids are materials that consist of metal atoms exclusively, giving them a unique set of properties. They are held together by a special type of bond called metallic bonding. This occurs when a lattice of positively charged metal ions is surrounded by a sea of delocalized electrons.