Assertion: Ostrich has vestigial wings and feather but is a cursorial animal.
Reason: Ostrich disused the wings for defence.

Options

A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
B. If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion.
C. If Assertion is true but the Reason is false.
D. If both Assertion and Reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Ostrich has vestigial wings and feathers but is a cursorial animal."
- This means that ostriches have wings that are not functional for flying (vestigial) and that they are adapted for running (cursorial).

2. **Defining Cursorial Animals**:
- Cursorial animals are those that are adapted specifically for running. They have physical traits that allow them to run fast or maintain a constant speed over long distances.

3. **Identifying Vestigial Structures**:
- Vestigial structures are remnants of organs or features that were once functional in an organism's ancestors but are no longer necessary for the current species.
- In the case of ostriches, their wings and feathers are considered vestigial because they do not serve the purpose of flight.

4. **Evaluating the Reason**:
- The reason states that "Ostrich disused the wings for defense."
- However, the primary reason ostriches do not use their wings for flight is due to their large size and heavy weight, which makes flying impossible.

5. **Conclusion**:
- The assertion is correct: ostriches do have vestigial wings and are cursorial animals.
- The reason is incorrect: ostriches do not use their wings for defense; rather, they have evolved to be non-functional for flight due to their size.

6. **Final Answer**:
- The assertion is true, but the reason is false.