ANS:C - N/m²

The unit of bulk modulus of elasticity for a liquid in SI units is N/m².

Explanation:

1. Bulk Modulus of Elasticity (K):
   • Bulk modulus is a measure of the compressibility of a substance when subjected to uniform pressure. It quantifies the resistance of a material to uniform compression.
   • For liquids, bulk modulus indicates how resistant the liquid is to being compressed or how much its volume changes under pressure.
2. SI Unit:
   • In the SI (International System of Units), the unit of pressure is the pascal (Pa), where 1 Pa=1 N/m21 \, \text{Pa} = 1 \, \text{N/m}^21Pa=1N/m2.
   • Therefore, bulk modulus, which is a ratio of stress to strain (both in pascals), has the unit of pascals (Pa).
3. Options Analysis:
   • N: Newton (N) is a unit of force.
   • N/m: Newton per meter (N/m) is a unit of linear density or force per unit length.
   • N/m²: Newton per square meter (N/m² or Pa) is the unit of pressure and also the unit for bulk modulus because it represents pressure per unit strain or change in volume.
   • N/m³: Newton per cubic meter (N/m³) is a unit of volumetric density.

Conclusion: