Answer: Option (a) is the correct answer.
Step-by-step explanation:
A solid substance has particles closer to each other because of strong intermolecular forces of attraction between them. Due to this reason these particles arrange themselves in an organized manner.
Hence, they tend to acquire fixed shape and volume.
For example, a tab;e, chair, pencil, black board etc are all solid substances.
Thus, we can conclude that particles are packed closely together in an organized way and maintain their set shape and volume, describes the characteristics of a solid.