Which of the following statements is true about glass? (a) Arrangement of silicate units is similar to that of liquid state. (b) Arrangement of silicate units is similar to that of solid state. (c) It has low viscosity and hence is not a true solid. (d) It has high viscosity with sharp melting point and hence is a solid.

Glass is an amorphous solid, which means it has a disordered atomic structure. It is typically formed by the rapid cooling of a liquid, which results in a rigid material with a non-crystalline arrangement of atoms. The constituent atoms are arranged in a manner that is intermediate between the highly ordered arrangement of a crystalline solid and the disordered arrangement of a liquid.

In a crystalline solid, the atoms or molecules are arranged in a regular, repeating pattern called a crystal lattice. In contrast, the arrangement of atoms or molecules in a liquid is disordered and lacks any long-range order. Being an amorphous solid, the arrangement of atoms in glass shows some short-range order (similar to a liquid) and also some rigidity (similar to a solid), but it does not have a long-range order like the crystalline solid.

Now let's analyze each of the given statements: (a) "Arrangement of silicate units is similar to that of liquid state." - This statement is partially true. While the arrangement of atoms in glass does have some short-range order (similar to a liquid), it also has some rigidity (similar to a solid). Thus, the arrangement of atoms in glass is not exactly like that in a liquid state, but it is intermediate between solid and liquid states. (b) "Arrangement of silicate units is similar to that of solid state." - This statement is not entirely correct because the arrangement of atoms in glass is not highly ordered like that in a crystalline solid. It is intermediate between solid and liquid states. (c) "It has low viscosity and hence is not a true solid." - This statement is incorrect. The viscosity of glass is high, as amorphous solids do not flow easily compared to liquids. However, it is true that glass is not a true crystalline solid because of its disordered atomic structure. (d) "It has high viscosity with sharp melting point and hence is a solid." - While it is true that glass has high viscosity, it does not have a sharp melting point. Instead, its transition from an amorphous solid to a liquid occurs over a temperature range.

Based on the analysis of the given statements, the most accurate statement is (a): "Arrangement of silicate units is similar to that of liquid state." However, it is important to understand that the arrangement of atoms in glass is not exactly like that in a liquid state, but it is intermediate between solid and liquid states, showing some properties of both.