The incorrect statement among the following is

Options

A. The entropy of the universe remains constant
B. Heat cannot be completely converted into work
C. This absolute entropy of a perfectly crystalline solid at absolute zero temperature is zero
D. The total energy of an isolated system remains constant

Explanation

To determine the incorrect statement among the provided options, we will analyze each statement based on the principles of thermodynamics.

### Step-by-Step Solution:

1. **Examine the First Option:**
- **Statement:** "The entropy of the universe remains constant."
- **Analysis:** According to the second law of thermodynamics, the entropy of the universe tends to increase over time. Therefore, this statement is incorrect.

2. **Examine the Second Option:**
- **Statement:** "Heat cannot be completely converted into work."
- **Analysis:** This statement is correct and aligns with the second law of thermodynamics, which states that not all heat energy can be converted into work due to inherent inefficiencies.

3. **Examine the Third Option:**
- **Statement:** "The absolute entropy of a perfectly crystalline solid at absolute zero temperature is zero."
- **Analysis:** This statement is correct and is a direct consequence of the third law of thermodynamics, which states that the entropy of a perfect crystal approaches zero as the temperature approaches absolute zero.

4. **Examine the Fourth Option:**
- **Statement:** "The total energy of an isolated system remains constant."
- **Analysis:** This statement is also correct and is a reflection of the law of conservation of energy, which states that the total energy in an isolated system does not change.

### Conclusion:
- The incorrect statement among the options is the first one: "The entropy of the universe remains constant."