Explanation:
Moulding sand is a mixture of sand, clay, water, and additives that is used to create moulds in the foundry industry. The water content in moulding sand plays a crucial role in determining its properties and performance.

Effect of Water Content on Flowability:
- Flowability refers to the ability of the moulding sand to flow and fill the mould cavity properly.
- An increase in water content in moulding sand leads to an increase in its flowability.
- This is because the water acts as a lubricant and reduces the friction between the sand particles, allowing them to slide past each other more easily.
- As a result, the moulding sand becomes more fluid and can flow through narrow gaps and corners in the mould cavity more efficiently.

Effect of Water Content on Permeability:
- Permeability refers to the ability of the moulding sand to allow gases and steam to escape during the casting process.
- An increase in water content in moulding sand reduces its permeability.
- This is because the excess water fills the gaps between the sand particles, reducing the interconnected voids and channels through which gases can escape.
- As a result, the moulding sand becomes less permeable, and gases and steam may get trapped inside the mould cavity, leading to defects in the casting.

Effect of Water Content on Compressive Strength:
- Compressive strength refers to the ability of the moulding sand to withstand applied pressure without breaking or deforming.
- An increase in water content in moulding sand reduces its compressive strength.
- This is because the excess water weakens the bonding between the sand particles, leading to a decrease in the overall strength of the moulding sand.
- As a result, the moulding sand becomes more prone to deformation and breakage when subjected to compressive forces.

Effect of Water Content on Strength:
- The term "strength" is broad and can refer to various properties such as tensile strength, shear strength, etc.
- Without specific information about the type of strength being referred to, it is difficult to determine the exact effect of water content.
- However, in general, an increase in water content tends to reduce the strength of moulding sand due to the weakening of particle bonding.

Conclusion:
Based on the given options, the correct answer is option 'B' - an increase in water content in moulding sand causes permeability to go through a maximum. This is because an increase in water content initially improves the flowability of the moulding sand, but beyond a certain point, it starts to reduce the permeability.