(A) Upward movement of food getting blocked.
(B) Downward movement of food getting blocked.
(C) Upward movement of water getting blocked.
(D) Downward movement of water getting blocked.

Explanation:

Change Observed in Set Up Y:
The given figure shows a set up at the start of experiment (X) and after a few days (Y). The change observed in set up Y is due to the growth of plants.

Reasons for the Change:
The change observed in set up Y can be attributed to the following factors:

1. Plant Growth:
The most significant reason for the change observed in set up Y is the growth of plants. Over the course of a few days, the plants in set up Y have grown taller and developed more leaves. This indicates that the plants are healthy and thriving.

2. Photosynthesis:
The growth of plants is primarily fueled by the process of photosynthesis. Through photosynthesis, plants convert sunlight, water, and carbon dioxide into glucose and oxygen. The glucose serves as a source of energy for the plants, while the oxygen is released into the atmosphere. As the plants in set up Y have grown, it implies that they have been able to carry out photosynthesis effectively.

3. Nutrient Absorption:
Another factor contributing to the change observed in set up Y is the absorption of nutrients by the plants. Plants require various nutrients, such as nitrogen, phosphorus, and potassium, for their growth and development. These nutrients are absorbed from the soil through the roots and transported to different parts of the plant. The presence of adequate nutrients in set up Y has allowed the plants to grow and flourish.

4. Water Supply:
Water is essential for the survival and growth of plants. It serves as a medium for nutrient absorption and is also required for various metabolic processes. The presence of a sufficient water supply in set up Y has provided the plants with the necessary hydration to support their growth.

5. Environmental Factors:
The growth of plants is also influenced by environmental factors such as temperature, light, and humidity. These factors can affect the rate of photosynthesis and overall plant growth. It is possible that the favorable environmental conditions in set up Y have contributed to the observed change.

Conclusion:
The change observed in set up Y is primarily due to the growth of plants. Factors such as photosynthesis, nutrient absorption, water supply, and environmental conditions have all played a role in supporting the growth and development of the plants.