The correct option is
A do not undergo clean cleavage when cut with a knife
Solids are of two types
(i) Crystalline
(ii) Amorphous
Amorphous solids does not have a definite geometrical shape.
Characteristic of amorphous solids:
1. They don’t have long-range repetitive internal structures that are found in crystals.
2. Regular patterns are scattered and in between the arrangement is disordered.
3. They are formed by sudden cooling of a liquid. Sometimes they are called supercooled liquids or pseudo solid
4. These are isotropic, which can show same physical properties in all directions.
5. They don't have sharp melting point due to the disordered arrangements. They have a range of temperature for melting.
6. They can be cut along random directions and have irregular surfaces. Thus, do not undergo clean cleavage with knife.
Thus, option (c) is correct.