A reference frame attached to the earth
a) is an inertial frame by definition
b) can not be an inertial frame because the earth is revolving around the sun
c) is an inertial frame because Newton's laws are applicable in this frame
d) cannot be an inertial frame because the earth is rotating about its axis

Options

A. a, b, c are correct
B. b only correct
C. b and d are correct
D. all are correct

Answer

To determine whether a reference frame attached to the Earth is an inertial frame, we need to analyze the motion of the Earth and the implications of that motion on the laws of physics, particularly Newton's laws.

### Step-by-Step Solution

1. **Understanding Inertial Frames**:
- An inertial frame is one in which an object at rest remains at rest, and an object in motion continues in uniform motion unless acted upon by a net external force. In such frames, Newton's laws of motion hold true.

2. **Motion of the Earth**:
- The Earth is not stationary; it is rotating about its own axis and revolving around the Sun. This means that the Earth is undergoing both rotational and circular motion.

3. **Effect of Earth's Motion**:
- Because the Earth is rotating, there is a centrifugal force experienced by objects on its surface. This force can cause deviations from the expected behavior of objects as described by Newton's laws.

4. **Evaluating the Options**:
- **Option A**: "is an inertial frame by definition" - This is incorrect because the Earth is in motion, and thus, it cannot be considered an inertial frame.
- **Option B**: "cannot be an inertial frame because the Earth is revolving around the Sun" - This is correct. The motion of the Earth around the Sun means that it is not an inertial frame.
- **Option C**: "is an inertial frame because Newton's laws are applicable in this frame" - This is incorrect. Since the Earth is accelerating (due to its rotation and revolution), Newton's laws do not apply in the same way they do in an inertial frame.
- **Option D**: "cannot be an inertial frame because the Earth is rotating about its axis" - This is also correct. The rotation of the Earth introduces additional forces that prevent it from being an inertial frame.

5. **Conclusion**:
- The correct options are B and D. Therefore, the reference frame attached to the Earth cannot be considered an inertial frame due to both its rotation and revolution.

### Final Answer:
The correct options are **B and D**.