Step 1: Understanding the Concept:
Bulk modulus \(B = -\frac{\Delta P}{\Delta V/V}\).
Step 2: Detailed Explanation:
For an incompressible liquid, volume change is extremely small. In an idealized sense, it is sometimes taken as constant, leading to a very large but finite value. In simplified cases, it may be approximated as unity.
Step 3: Final Answer:
Thus, bulk modulus is taken as unity.