In slush casting, a hollow casting with thin walls is produced. Slush casting is a type of casting process that involves pouring a liquid material, usually a metal alloy, into a hollow mold. The mold is then rotated or tilted to coat the inner surfaces of the mold with the liquid material. As the material solidifies, excess material is poured out, leaving behind a hollow casting with thin walls.

Here is a detailed explanation of why option B is the correct answer:

Slush casting process:
1. Mold preparation: The mold used in slush casting is typically made of a heat-resistant material, such as silicone or rubber. The mold is designed in the shape of the desired casting, with hollow cavities and thin walls.

2. Material pouring: The liquid material, usually a metal alloy, is poured into the mold. The mold is then rotated or tilted to ensure that the liquid material coats the inner surfaces of the mold evenly.

3. Solidification: As the liquid material comes into contact with the cooler mold surfaces, it begins to solidify. The rotation or tilting of the mold helps to distribute the material evenly and create a uniform thickness of the casting walls.

4. Excess material removal: After a certain period of time, when the desired wall thickness has been achieved, the excess material is poured out of the mold. This is done while the casting is still in a partially solidified state, allowing the remaining material to form a hollow structure with thin walls.

Advantages of slush casting:
- Hollow castings: Slush casting is particularly suitable for producing hollow castings, as the liquid material can flow into the cavities and create the desired shape.
- Thin walls: The rotation or tilting of the mold helps to create castings with thin walls. This is beneficial for applications where lightweight structures are required.

Other options:
a) Hollow castings with thick walls: Slush casting is not suitable for producing castings with thick walls. The rotation or tilting of the mold helps to distribute the material evenly and create thin walls.
c) Thin castings: While slush casting can produce castings with thin walls, it is not limited to thin castings only. The thickness of the casting walls can be adjusted based on design requirements.
d) Thick castings: As mentioned earlier, slush casting is not suitable for producing castings with thick walls. The process is more suitable for creating hollow castings with thin walls.

In conclusion, slush casting is a process that is used to produce hollow castings with thin walls. The liquid material is poured into a mold, which is then rotated or tilted to coat the inner surfaces of the mold. As the material solidifies, excess material is poured out, leaving behind a hollow casting with thin walls.