Explanation:
When irrigation water is supplied to crops, it has a direct impact on their yield. However, the relationship between the amount of irrigation water and crop yield is not linear. It follows a certain pattern, which can be explained by the concept of the yield response curve.

Yield Response Curve:
The yield response curve is a graphical representation of the relationship between the amount of irrigation water applied and the resulting crop yield. It shows how the yield of crops changes with increasing amounts of irrigation water.

Increasing Yield:
Initially, when irrigation water is supplied to crops, the yield increases. This is because water is a crucial factor for plant growth and development. It helps in the absorption of nutrients, photosynthesis, and overall plant metabolism. Therefore, an increase in irrigation water leads to better plant growth and increased crop yield.

Optimum Yield:
However, as the amount of irrigation water continues to increase, there comes a point where the crop yield reaches its maximum potential. This is known as the optimum yield point. At this point, the crop is receiving the ideal amount of water for its growth and water requirements. Any additional increase in irrigation water beyond this point does not result in a significant increase in crop yield.

Decreasing Yield:
In fact, supplying excessive amounts of irrigation water can have negative effects on crop yield. It can lead to waterlogging, which deprives the plants of oxygen and hampers their root growth. Furthermore, it can also leach away essential nutrients from the soil, reducing their availability to the plants. These adverse effects ultimately result in a decrease in crop yield.

Conclusion:
In summary, the relationship between supplied irrigation water and crop yield follows a yield response curve. Initially, the yield increases with increasing irrigation water, but it reaches a maximum limit at the optimum yield point. Beyond this point, the yield starts to decrease due to the adverse effects of excessive water. Therefore, the correct answer to the given question is option 'D' - the yield increases up to a certain limit and then decreases.