The incorrect statement according to second law of themodynamics is

Options

A. Heat cannot flow from colder body to a hotter body of its own
B. All spontaneous processes are thermody-namically irreversible
C. Heat can be converted into work completely without causing some permanent change in the system (or) surroundings
D. Perpetual motion machine of second kind is not possible

Answer

To solve the question regarding the incorrect statement according to the second law of thermodynamics, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Second Law of Thermodynamics**:
The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. It implies that heat cannot spontaneously flow from a colder body to a hotter body.

2. **Analyzing Option A**:
- **Statement**: "Heat cannot flow from a colder body to a hotter body by itself."
- **Evaluation**: This statement is true according to the second law. Heat naturally flows from a hot body to a cold body, not the other way around.

3. **Analyzing Option B**:
- **Statement**: "All spontaneous processes are thermodynamically irreversible."
- **Evaluation**: This statement is also true. In nature, spontaneous processes tend to proceed in one direction and cannot be reversed without external work.

4. **Analyzing Option C**:
- **Statement**: "Heat cannot be converted into work completely without causing some permanent change in the system or surroundings."
- **Evaluation**: This statement is true. According to the second law, not all heat can be converted into work; some energy is always lost to the surroundings, making complete conversion impossible.

5. **Analyzing Option D**:
- **Statement**: "Perpetual motion machine of the second kind is not possible."
- **Evaluation**: This statement is true. A perpetual motion machine of the second kind would violate the second law of thermodynamics as it would convert thermal energy into work without any loss, which is impossible.

6. **Conclusion**:
After evaluating all options, we find that:
- Option A: True
- Option B: True
- Option C: True
- Option D: True
- However, the statement in Option C is misleading as it suggests that heat can be converted into work completely, which is incorrect. Therefore, the incorrect statement according to the second law of thermodynamics is **Option C**.

### Final Answer:
The incorrect statement according to the second law of thermodynamics is **Option C**.