Which of the following statements is true

Options

A. The total entropy of the universe remains constant
B. The total entropy of the universe is continuously decreasing
C. The total energy of the universe is continuously decreasing
D. The total energy of the universe remains constant

Answer

To determine which of the statements is true, we can analyze each statement based on the principles of thermodynamics.

### Step-by-Step Solution:

1. **Evaluate the First Statement: "The total entropy of the universe remains constant."**
- According to the second law of thermodynamics, the total entropy of the universe tends to increase over time. In isolated systems, entropy can only remain constant in reversible processes, which are ideal and do not occur in real life. Therefore, this statement is **false**.

2. **Evaluate the Second Statement: "The total entropy of the universe is continuously decreasing."**
- Again, referencing the second law of thermodynamics, entropy is never decreasing in an isolated system. It can only stay the same in reversible processes or increase in irreversible processes. Thus, this statement is also **false**.

3. **Evaluate the Third Statement: "The total energy of the universe is continuously decreasing."**
- According to the first law of thermodynamics, energy cannot be created or destroyed; it can only be transformed from one form to another. Therefore, the total energy of the universe remains constant. This statement is **false**.

4. **Evaluate the Fourth Statement: "The total energy of the universe remains constant."**
- As per the first law of thermodynamics, the total energy of an isolated system (the universe) is conserved. It does not increase or decrease but remains constant. Therefore, this statement is **true**.

### Conclusion:
The correct answer is that the total energy of the universe remains constant.