Assertion: `MnO` is basic whereas `Mn_2O_7` is acidic.
Reason: Higher the oxidation state of a transition metal in its oxide, greater is the acidic character.

Options

A. If both (A) and (R) are correct and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct, but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect but (R) is correct.

Answer

To analyze the assertion and reason provided in the question, we will break down the concepts step by step.

### Step 1: Understanding the Assertion
The assertion states that `MnO` is basic while `Mn2O7` is acidic.

- **MnO**: In this compound, manganese (Mn) is in the +2 oxidation state. Basic oxides typically form when the metal is in a lower oxidation state. In this case, MnO can donate electrons, which is characteristic of basic behavior.

- **Mn2O7**: In this compound, manganese is in the +7 oxidation state. Higher oxidation states in transition metal oxides tend to exhibit acidic properties. Thus, Mn2O7 can accept protons (H+) and behave as an acid.

### Step 2: Understanding the Reason
The reason provided states that the higher the oxidation state of a transition metal in its oxide, the greater the acidic character.

- This statement is generally true for transition metals. As the oxidation state increases, the ability of the metal to attract electrons increases, leading to a stronger tendency to form acidic oxides.

### Step 3: Conclusion
Both the assertion and the reason are correct. The assertion correctly identifies the basic nature of MnO and the acidic nature of Mn2O7, while the reason accurately explains the relationship between oxidation state and acidic character.

### Final Answer
Both the assertion and the reason are correct, and the reason is the correct explanation for the assertion.