In a green sand moulding process, uniform ramming leads to a uniform flow of molten metal into the mould cavity. This is because uniform ramming ensures that the sand is evenly compacted and distributed throughout the mould, providing consistent resistance for the molten metal as it fills the cavity.

Uniform Flow of Molten Metal into the Mould Cavity:
- When the sand is uniformly rammed, it creates a consistent density and compaction throughout the mould. This allows the molten metal to flow smoothly and evenly through the mould cavity.
- If the sand is not uniformly rammed, there can be variations in density and compaction, leading to uneven flow of molten metal. This can result in incomplete filling of the mould cavity, leading to defects in the casting.

Importance of Uniform Flow:
- Uniform flow of molten metal is important for achieving accurate and consistent shape and dimensions of the casting. When the molten metal flows uniformly, it fills the entire mould cavity, resulting in a casting with precise dimensions.
- If there are variations in the flow of metal, it can result in uneven filling of the mould cavity, leading to dimensional inconsistencies and defects in the casting.

Other Benefits of Uniform Ramming:
- Less Chance of Gas Porosity: Uniform ramming helps in minimizing the formation of gas porosity in the casting. Gas porosity occurs when gases trapped within the mould are not able to escape during the casting process. Uniform ramming helps in creating a more compact and dense mould, reducing the chances of gas entrapment.
- Greater Dimensional Stability of the Casting: Uniform ramming ensures that the mould maintains its shape and dimensions during the casting process. This leads to greater dimensional stability of the casting, reducing the need for post-casting machining or corrections.
- Less Sand Expansion Type of Casting Defect: Uniform ramming helps in minimizing the occurrence of sand expansion defects in the casting. Sand expansion defects occur when the sand expands due to the heat of the molten metal, causing the casting to crack or distort. Uniform ramming ensures that the sand is evenly compacted, reducing the likelihood of sand expansion defects.

In conclusion, in a green sand moulding process, uniform ramming is important for achieving a uniform flow of molten metal into the mould cavity. This leads to accurate dimensions, reduced defects, and improved casting quality.

Answer of this question is option 'c'