`CH_(3)CH_(2)underset(CH_(3))underset(|)(C)=CHCH_(3)overset("Reagent")toCH_(3)CH_(2)underset(CH_(3))underset(|)(CH)overset(OH)overset(|)(CH)CH_(3)`
Which reagent forms the above organic product as the single product in the above reaction?

Options

A. `H_(2)O //H^(+)`
B. `(Hg(OCOCH_(3))_(2),H_(2)O)/(NaBH_(4))`
C. `(B_(2)H_(6),THF)/(NaOH,H_(2)O_(2))`
D. `KMnO_(4)//OH^(-)//"Cold"`

Explanation

To determine which reagent forms the given organic product as a single product, we need to analyze the structure of the reactant and the product. The reactant is a substituted alkene, and the product is a secondary alcohol.

1. **Identify the structure of the reactant and product**:
- The reactant is a substituted alkene with a double bond between the second and third carbon atoms, and a methyl group attached to the third carbon.
- The product is a secondary alcohol with the hydroxyl group (OH) on the second carbon.

2. **Consider the reagents**:
- **Option A: Simple Hydration**: This involves adding water (H2O) across the double bond. According to Markovnikov's rule, the hydrogen will add to the less substituted carbon, which would lead to a tertiary alcohol, not a secondary alcohol.
- **Option B: Oxymercuration-Demercuration**: This method involves the addition of mercuric acetate followed by reduction. The reaction proceeds through a cyclic mercurinium ion, leading to Markovnikov addition. This would yield a secondary alcohol, as the nucleophile (water) would attack the more substituted carbon.
- **Option C: Hydroboration-Oxidation**: This method typically results in anti-Markovnikov addition and is not suitable for this structure since it is a non-terminal alkene. Therefore, it would not yield the desired product.
- **Option D: Baeyer's Reagent (KMnO4)**: This reagent oxidizes alkenes to diols, resulting in the formation of a glycol, which is not the desired product.

3. **Conclusion**:
- After analyzing all options, **Option B (Oxymercuration-Demercuration)** is the only reagent that will yield the secondary alcohol as a single product.

### Final Answer:
The reagent that forms the above organic product as the single product in the reaction is **Option B: Oxymercuration-Demercuration**.