Assertion`:-` A particle on earth found to be at rest when seen from a frame `U_(1)` and moving with a constant velocity when seen from another frame `U_(2)`. Then both frames may be non`-`inertial.
Reason `:-` A reference frame attached to the earth must be an inertial frame.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertiion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are False

Explanation

To solve the given question, we need to analyze the assertion and reason provided.

### Step 1: Understand the Assertion
The assertion states that a particle on Earth is at rest in one frame (U1) and moving with a constant velocity in another frame (U2). This situation suggests that both frames could potentially be non-inertial.

### Step 2: Analyze the Concept of Inertial and Non-Inertial Frames
An inertial frame is one in which Newton's laws of motion hold true without any fictitious forces acting on the objects. A non-inertial frame is one that is accelerating, and in such frames, fictitious forces must be considered to apply Newton's laws.

### Step 3: Evaluate the Condition of the Particle
- In frame U1, the particle is at rest, which means its velocity is 0.
- In frame U2, the particle is moving with constant velocity. This indicates that frame U2 is either moving uniformly or is in a non-inertial frame where the particle appears to move due to the acceleration of the frame itself.

### Step 4: Consider the Possibility of Both Frames Being Non-Inertial
The assertion suggests that both frames may be non-inertial. This is plausible if both frames are accelerating at the same rate. In such a case, the relative motion between the particle and the frames can lead to the observed conditions.

### Step 5: Understand the Reason
The reason states that a reference frame attached to the Earth must be an inertial frame. However, this is misleading because the Earth is not a perfect inertial frame due to its rotation and other accelerative effects (like gravitational variations).

### Step 6: Conclusion
- The assertion is true because it is indeed possible for both frames to be non-inertial.
- The reason is false because the Earth, while often treated as an inertial frame for simplicity, is not a perfect inertial frame due to its rotation and other factors.

### Final Answer
- Assertion: True
- Reason: False
- Therefore, the correct conclusion is that the assertion is true while the reason is false.