Assertion (A): In `BrF_(3)` oxidastion state of F is +3.
Reason R: Electronegativity of F is more than that of Bromine.

Options

A. A & R are true, R is correct explanation of A
B. A & R are true, R is not correct explanation of A
C. A is true, but R is false
D. A is false, but R is true

Explanation

To solve the question regarding the assertion and reason provided, we need to analyze both statements carefully.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that in `BrF3`, the oxidation state of F is +3.
- To determine the oxidation state of fluorine in `BrF3`, we need to recall that fluorine is the most electronegative element and typically has an oxidation state of -1 in compounds.

2. **Calculating the Oxidation State of Bromine (Br)**:
- In `BrF3`, there are three fluorine atoms. Since each fluorine has an oxidation state of -1, the total contribution from fluorine is:
\[ 3 \times (-1) = -3 \]
- Let the oxidation state of bromine be \( x \). The overall charge of the molecule is neutral (0), so we can set up the equation:
\[ x + (-3) = 0 \]
- Solving for \( x \):
\[ x - 3 = 0 \implies x = +3 \]
- Therefore, the oxidation state of bromine (Br) is +3, and the oxidation state of fluorine (F) is -1, not +3.

3. **Understanding the Reason (R)**:
- The reason states that the electronegativity of F is more than that of bromine.
- This statement is true. Fluorine is indeed more electronegative than bromine, which explains why fluorine typically has a negative oxidation state in compounds.

4. **Conclusion**:
- Since the assertion (A) is false (the oxidation state of F in `BrF3` is -1, not +3), and the reason (R) is true (fluorine is more electronegative than bromine), we conclude that:
- Assertion (A) is false.
- Reason (R) is true.

5. **Final Answer**:
- The correct answer is that Assertion (A) is false, and Reason (R) is true. Therefore, the correct option is D.