Mark the correct statement(s).

Options

A. (a) The work-energy theorem is valid only for particles
B. (b) The work-energy theorem is an invariant law of physics.
C. (c) The work-energy theorem is valid only in inertial frames of reference.
D. (d) The work-energy theorem can be applied in non-inertial frames of reference too.

Explanation

To solve the question of marking the correct statements regarding the work-energy theorem, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement A: The work-energy theorem is valid only for particles.**
- The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy. This theorem is not limited to just particles; it can be applied to systems of particles as well. Therefore, this statement is **incorrect**.

2. **Statement B: The work-energy theorem is an invariant law of physics.**
- The work-energy theorem holds true in various contexts and can be applied universally to different systems, whether they are particles or collections of particles. Thus, this statement is **correct**.

3. **Statement C: The work-energy theorem is valid only in inertial frames of reference.**
- The work-energy theorem can be applied in both inertial and non-inertial frames of reference. While it may be more complicated to apply in non-inertial frames due to the presence of fictitious forces, it is still valid. Therefore, this statement is **incorrect**.

4. **Statement D: The work-energy theorem can be applied in non-inertial frames of reference.**
- As mentioned, the work-energy theorem is indeed applicable in non-inertial frames, although it may require additional considerations due to the effects of fictitious forces. Thus, this statement is **correct**.

### Final Conclusion:
The correct statements are **B** and **D**.