a) Dams and reserviors transfer water through areas of deficit using canals and underground pipes.
b) Water shed provides water for constructions.

Explanation

**Step-by-Step Solution:**

1. **Understanding Statement A**: The first statement mentions that "dams and reservoirs transfer water through areas of deficit using canals and underground pipes." This statement is true. Dams and reservoirs are constructed to store water and manage its distribution, especially in areas where water is scarce. They help in transferring water to regions that require it, using various methods such as canals and underground pipes.

2. **Understanding Statement B**: The second statement states that "watershed provides water for constructions." This statement is incorrect. A watershed is an area of land that drains rainwater and snow into a common outlet, such as a river or lake. While watersheds are crucial for maintaining water supply and supporting ecosystems, they are not primarily designed to provide water specifically for construction purposes. Instead, they support wildlife habitats and provide water for agricultural and natural ecosystems.

3. **Conclusion**: Based on the analysis, we conclude that Statement A is correct, while Statement B is incorrect.

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