In the reaction with HCl, an alkene reacts in accordance with Markownikoff's rule to give a product 1-chloro-1-methylcyclohexane. The possible alkene is:

Options

A.
B.
C. both (A) and (B)
D.

Answer

To determine the possible alkene that reacts with HCl to yield 1-chloro-1-methylcyclohexane according to Markownikoff's rule, we need to analyze the structure of the product and the implications of the rule.

### Step-by-Step Solution:

1. **Identify the Product Structure**:
The product is 1-chloro-1-methylcyclohexane. This indicates that we have a cyclohexane ring with a chlorine (Cl) and a methyl (CH₃) group both attached to the same carbon (the first carbon in the ring).

2. **Understand Markownikoff's Rule**:
Markownikoff's rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom (H) will attach to the carbon with the greater number of hydrogen atoms already attached, while the halogen (Cl in this case) will attach to the carbon with fewer hydrogen atoms.

3. **Analyze the Possible Alkenes**:
We need to find an alkene that, when reacted with HCl, will lead to the formation of the product. The alkene must have a structure that allows for the addition of HCl to yield the desired product.

4. **Consider the Structure of Cyclohexane**:
Cyclohexane has six carbon atoms in a ring. The presence of a methyl group on one of the carbons indicates that this carbon is already bonded to one additional carbon (the methyl group) and will have fewer hydrogen atoms compared to the adjacent carbon.

5. **Determine the Alkene**:
- If we consider a possible alkene such as 1-methylcyclohexene, the double bond is between the carbon that has the methyl group and an adjacent carbon.
- When HCl is added, according to Markownikoff's rule, Cl will attach to the carbon of the double bond that has fewer hydrogens (the one with the methyl group), and H will attach to the other carbon, leading to the formation of 1-chloro-1-methylcyclohexane.

6. **Verify Other Options**:
- Check other potential alkenes (like 3-methylcyclohexene or 2-methylcyclohexene) to see if they can also yield the same product.
- For instance, 3-methylcyclohexene would not yield the desired product because the addition of HCl would not follow Markownikoff's rule correctly to give 1-chloro-1-methylcyclohexane.

7. **Conclusion**:
The possible alkenes that can react with HCl to yield 1-chloro-1-methylcyclohexane are those that allow for the addition of HCl according to Markownikoff's rule, specifically 1-methylcyclohexene.

### Final Answer:
The possible alkene is **1-methylcyclohexene**.