Assertion `:` trans `-2-`Butene on reaction with `Br_(2)` gives meso`-2,3-`dibromobutane.
Reason `:` The reaction involves syn`-`addition of bromine.

Options

A. If the 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 reason is false
D. If both assertion and reason are false statements.

Explanation

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

### Assertion:
Trans-2-butene reacts with Br₂ to give meso-2,3-dibromobutane.

### Reason:
The reaction involves syn-addition of bromine.

### Step-by-Step Solution:

1. **Understanding the Structure of Trans-2-butene**:
- Trans-2-butene has the structure:
```
CH3-CH=CH-CH3
```
- The double bond is between the second and third carbon atoms, and the two methyl groups (CH3) are on opposite sides of the double bond.

2. **Reaction with Bromine (Br₂)**:
- When trans-2-butene reacts with bromine, it undergoes an electrophilic addition reaction.
- The double bond attacks a bromine molecule, leading to the formation of a cyclic bromonium ion intermediate.

3. **Formation of the Cyclic Bromonium Ion**:
- The bromonium ion is formed as follows:
```
CH3-CH(Br)-CH(Br)-CH3
```
- In this intermediate, one bromine atom is bonded to one carbon of the double bond, and the other carbon has a positive charge.

4. **Attack of Bromide Ion**:
- The bromide ion (Br⁻) can attack the cyclic bromonium ion from the opposite side (backside attack), leading to anti-addition.
- This results in the formation of 2,3-dibromobutane.

5. **Checking for Meso Compound**:
- The product formed is meso-2,3-dibromobutane. A meso compound has an internal plane of symmetry.
- The structure of meso-2,3-dibromobutane can be represented as:
```
CH3-CH(Br)-C(Br)-CH3
```
- The two bromine atoms are on opposite sides, and there is a plane of symmetry between the two halves of the molecule.

6. **Conclusion on Assertion**:
- The assertion is true: trans-2-butene does yield meso-2,3-dibromobutane upon reaction with Br₂.

7. **Analyzing the Reason**:
- The reason states that the reaction involves syn-addition of bromine. However, the addition of bromine to alkenes is typically anti-addition due to the formation of the bromonium ion.
- Therefore, the reason is false.

### Final Conclusion:
- The assertion is true, but the reason is false. Thus, the correct option is that the assertion is true, but the reason is false.