The correct option is C Crystalline solids give irregular cleavage whereas amorphous solids can be cleaved along definite planes.
In crystalline solids the particles (atoms, ions, or molecules) are orderly arranged thus these have characteristic geometry while amorphous solids do not have characteristic geometry. A crystalline solid has a sharp melting point, i.e., it changes into liquid state at a fixed temperature, whereas an amorphous solid does not have a sharp melting point.