Solids are often defined as having a definite shape, while gases and liquids have no definite shape. this can best be explained by the fact that
a) solids have a more ordered arrangement of atoms than liquids and gases.
b) in solids molecules move faster than in liquids or gases.
eliminate
c) solids have less internal energy than liquids and gases.
d) solids have the least orderly internal structure.

Option (A) is the correct answer.

Explanation:

In solids, there occurs strong intermolecular forces of attraction between the molecules. Due to this they are not able to move from their position but they can vibrate at their mean position.

Hence, they are held in an ordered arrangement with each other. As a result, they have definite shape and volume.

On the other hand in a liquid, molecules have more kinetic energy as compared to molecules of a solid. Hence, liquid molecules are able to slide past each other due to which they take the shape of container in which they are placed.

In gases, molecules have high kinetic energy. Hence, they tend to move randomly from one place to another. That is why, gases occupy the volume of container in which they are placed.

Thus, we can conclude that the statement solids have a more ordered arrangement of atoms than liquids and gases best explains why solids have a definite shape.

thermal energy is the answer