Non-crystalline solids, also known as amorphous solids, do not have a regular and ordered arrangement of particles. They lack a long-range order characteristic of crystalline solids. The arrangement of particles in non-crystalline solids is more random, giving them a disordered structure.

Among the options provided, the non-crystalline solid is (D) Plastic. Let's discuss each option in detail:

(A) P4O10:
P4O10 is a compound known as tetraphosphorus decoxide. It consists of four phosphorus atoms and ten oxygen atoms. It forms a crystalline structure with a regular arrangement of atoms. Therefore, it is a crystalline solid.

(B) P4:
P4 is a molecule called phosphorus. It consists of four phosphorus atoms bonded together. It forms a tetrahedral structure with a regular arrangement of atoms. Therefore, it is a crystalline solid.

(C) Graphite:
Graphite is a form of carbon that consists of layers of carbon atoms arranged in a hexagonal lattice. Each carbon atom is bonded to three other carbon atoms, forming a planar structure. Although graphite has a layered structure, it still possesses a long-range order, making it a crystalline solid.

(D) Plastic:
Plastic is a synthetic material made up of long chains of polymers. These chains are randomly intertwined and have a disordered arrangement. This lack of order makes plastic a non-crystalline or amorphous solid. Plastic can be molded into various shapes due to its flexible and disordered structure.

In conclusion, among the given options, plastic (option D) is a non-crystalline solid. It does not have a regular arrangement of particles and exhibits a disordered structure.