The product formed in the following chemical reaction is :

The correct option is Option 4.

Step-by-Step Explanation:

1. Analysis of the Reactant:
The starting material shown in the question contains two key functional groups:

• A cyclic ketone (carbonyl group, C=O) on the cyclohexane ring.
• An ester group ($-{\mathrm{CH}}_2-C(=O)-{\mathrm{OCH}}_3$) attached at position 2 of the ring.

There is also a methyl group ($-{\mathrm{CH}}_3$) at position 3 of the ring.

2. Reagent and Chemoselectivity:
The reagent used in this reaction is sodium borohydride (${\mathrm{NaBH}}_4$) in ethanol ($C_2{H}_5\mathrm{OH}$).

• ${\mathrm{NaBH}}_4$ is a mild and highly selective reducing agent.
• It selectively reduces aldehydes and ketones to their corresponding alcohols.
• Under normal conditions, ${\mathrm{NaBH}}_4$ does not reduce ester groups ($-{\mathrm{COOCH}}_3$) because esters are less electrophilic and less reactive toward hydride attack compared to ketones.

3. Determination of the Product:
Because of this chemoselectivity:

• The ketone group on the cyclohexane ring is reduced to a secondary alcohol group ($-\mathrm{OH}$).
• The ester side chain ($-{\mathrm{CH}}_2{\mathrm{COOCH}}_3$) remains completely unaffected.

Therefore, the final product consists of a cyclohexanol ring with the ester group and methyl group intact, which corresponds to the structure shown in Option 4.