Answer:

There are two forms of solid which can exist above and below a critical temperature. These forms are known as crystalline and amorphous solids. Let's discuss each of them in detail:

1. Crystalline Solids:
Crystalline solids have a well-defined, ordered arrangement of atoms or molecules in a repeating pattern called a crystal lattice. They have a highly regular structure with long-range order, meaning that the arrangement of particles repeats periodically over a large distance. Examples of crystalline solids include salt, diamonds, and quartz.

Key Points:
- Crystalline solids have a well-defined, ordered arrangement of atoms or molecules.
- They have a highly regular structure with long-range order.
- The arrangement of particles repeats periodically over a large distance.

2. Amorphous Solids:
Amorphous solids, on the other hand, do not have a well-defined, ordered arrangement of particles. They lack long-range order and have a more random, disordered structure. Amorphous solids are characterized by a lack of crystalline symmetry. Examples of amorphous solids include glass, rubber, and plastic.

Key Points:
- Amorphous solids do not have a well-defined, ordered arrangement of particles.
- They lack long-range order and have a more random, disordered structure.
- Amorphous solids are characterized by a lack of crystalline symmetry.

Explanation:
Above and below a certain temperature called the critical temperature, both crystalline and amorphous forms of solids can exist. The critical temperature is the temperature at which a solid undergoes a phase transition from one form to another. For example, when heating a crystalline solid, it may reach its critical temperature and transform into an amorphous solid. Similarly, cooling an amorphous solid below its critical temperature can cause it to crystallize.

The existence of both forms of solids above and below the critical temperature is due to the arrangement and behavior of the particles within the solid. Crystalline solids have a more ordered structure, whereas amorphous solids have a more disordered structure. The arrangement of particles determines the physical properties and behavior of the solid, including its ability to exist in different forms.

In conclusion, the two forms of solid which can exist above and below a critical temperature are crystalline and amorphous solids. Crystalline solids have a regular, ordered arrangement of particles, while amorphous solids have a more random, disordered structure. The existence of both forms is determined by the critical temperature at which phase transitions occur.

Option D.... one dimension