Assertion : `CH_3-overset(Br)overset(|)(CH)-CH_2CH_3` on reaction with alcoholic KOH gives `CH_3CH=CHCH_3` as a result of dehydrohalogenation.
Reason : Elimination reaction takes place in accordance with Markovnikov's rule.

Options

A. If both assertion and reason are true and reason Is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assetion is true but reason is false.
D. If both assertion and reason are false.

Explanation

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that the compound `CH3-CH(Br)-CH2-CH3` (which is 3-bromobutane) reacts with alcoholic KOH to yield `CH3-CH=CH-CH3` (which is butene).
- This reaction is a type of elimination reaction known as dehydrohalogenation, where a hydrogen halide (HBr in this case) is eliminated from the haloalkane.

2. **Reaction Mechanism**:
- In the elimination reaction, the bromine atom (Br) is removed along with a hydrogen atom (H) from an adjacent carbon atom.
- This results in the formation of a double bond between the two carbon atoms, leading to the formation of an alkene.

3. **Identifying the Product**:
- The possible products from the elimination can be:
- If H is removed from the carbon adjacent to Br (C2), the product will be `CH3-CH=CH-CH3` (2-butene).
- If H is removed from the other adjacent carbon (C3), the product will be `CH2=CH-CH2-CH3` (1-butene).
- However, the more stable product (major product) is 2-butene because it is a more substituted alkene compared to 1-butene.

4. **Understanding the Reason**:
- The reason states that the elimination reaction takes place in accordance with Markovnikov's rule.
- Markovnikov's rule applies to addition reactions, not elimination reactions. In elimination reactions, we refer to Zaitsev's rule (or Saytzeff's rule), which states that the more substituted alkene is the major product.

5. **Conclusion**:
- The assertion is true because the reaction does yield 2-butene as a product of dehydrohalogenation.
- The reason is false because Markovnikov's rule does not apply to elimination reactions; instead, Zaitsev's rule is applicable.
- Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- The correct option is: **Assertion is true, but Reason is false.**