• Amorphous solids usually have definite values of various physical properties like mechanical strength or refractive index, electrical conductivity etc.(isotropic not anisotropic) through all the directions. This is due to lack of long-range repetitive arrangement or order unlike crystalline solids; arrangement of particles is indefinite in different directions (x,y & z planes) which results in an overall equivalent arrangement in all directions, therefore giving birth to isotropicity and the value of physical properties will be same along all directions.

• Other 3 options (i) On heating they may become crystalline at certain temperature , (ii) They may become crystalline on keeping for long time and

(iii) Amorphous solids can be moulded by heating are possible cases for amorphous solids.