The concept of degrees of freedom is an important one in thermodynamics. It refers to the number of independent variables that can be used to describe the state of a system. In the case of water and ice, the number of degrees of freedom is determined by the number of variables that are required to specify the state of the system.

Explanation:

- Degrees of freedom refer to the number of independent variables that can be used to describe the state of a system.
- In the case of water and ice, the number of degrees of freedom is determined by the number of variables that are required to specify the state of the system.
- When water and ice are in equilibrium, they exist in a state of coexistence where the temperature, pressure, and composition are constant.
- In this state, there is one independent variable that can be changed without changing the state of the system.
- This variable is the chemical potential of the water, which is the amount of energy that is required to add or remove a molecule of water from the system.
- Therefore, the number of degrees of freedom of liquid water in equilibrium with ice is one.

Conclusion:

The correct answer is option 'B' because the number of degrees of freedom of liquid water in equilibrium with ice is one.