Fluidity is greatly influenced by:

a) Carbon content in molten metal
The carbon content in molten metal does have an effect on its fluidity to some extent. Carbon acts as a flux and can reduce the melting point of certain metals, making them more fluid. However, the influence of carbon content on fluidity is not as significant as other factors.

b) Pouring temperature of molten metal
The pouring temperature of molten metal is the most critical factor that significantly influences its fluidity. Fluidity refers to the ability of a molten metal to flow and fill the mold cavity during the casting process. When the pouring temperature is too low, the molten metal may solidify prematurely, resulting in poor fluidity and incomplete filling of the mold. On the other hand, if the pouring temperature is too high, the molten metal may become excessively fluid, leading to issues such as metal splashing or erosion of the mold walls. Therefore, maintaining the correct pouring temperature is crucial to achieve optimal fluidity during casting.

c) Inoculation added
Inoculation refers to the addition of certain elements or compounds to molten metal to modify its microstructure and improve its properties. While inoculation can have various effects on the metal, such as refining the grain structure or enhancing the mechanical properties, it does not have a direct influence on fluidity. Therefore, inoculation does not greatly affect the fluidity of molten metal.

Correct answer: Option B) Pouring temperature of molten metal

Explanation:
The pouring temperature of molten metal plays a crucial role in determining its fluidity during the casting process. It directly affects the viscosity and flow characteristics of the molten metal, determining how well it can fill the mold cavity. By adjusting the pouring temperature, foundry workers can control the fluidity of the molten metal and ensure that it flows smoothly and evenly throughout the mold. This is essential for producing high-quality castings with consistent dimensions and properties. Therefore, out of the given options, the pouring temperature of molten metal is the most significant factor influencing fluidity.