Precision casting, also known as investment casting, is a manufacturing process used to create complex and intricate metal parts with high dimensional accuracy and smooth surface finish. In this process, a pattern is used to create a mold, into which molten metal is poured.

The pattern is typically made from a material that can be easily shaped and then removed from the mold without damaging it. The choice of pattern material depends on factors such as the complexity of the part, the desired surface finish, and the type of metal being cast.

Let's analyze the given options to determine which pattern-materials are used in precision casting:

1. Plaster of Paris:
Plaster of Paris is a common material used for making patterns in precision casting. It is a type of gypsum plaster that can be easily molded and has good dimensional stability. Plaster of Paris patterns are inexpensive and can be used for both small and large castings. However, they are not suitable for high-temperature applications as they can degrade when exposed to heat.

2. Plastics:
Plastics, such as polystyrene and polyethylene, are widely used for making patterns in precision casting. They are lightweight, can be easily molded into complex shapes, and have good dimensional stability. Plastic patterns are cost-effective and can be used for both small and large castings. They are also suitable for high-temperature applications as they can withstand the heat during the casting process.

3. Anodized Aluminium Alloy:
Anodized aluminium alloy is not commonly used as a pattern material in precision casting. Anodizing is an electrochemical process that enhances the corrosion resistance and surface hardness of aluminium. While anodized aluminium can be used for certain applications, it is not an ideal choice for making patterns as it is difficult to shape and remove from the mold without causing damage.

4. Frozen Mercury:
Frozen mercury is not used as a pattern material in precision casting. Mercury is a toxic heavy metal that is liquid at room temperature. It is not suitable for making patterns as it cannot be easily shaped or removed from the mold without causing contamination and safety hazards.

Based on the analysis, the correct answer is option 'B' (2 and 4) - Plastics and Frozen Mercury are not used as pattern materials in precision casting.