Complete the following equation:

The correct answer is option 3.

The given reactant is 3-Oxobutanoic acid and the reagents and catalysts shows that it is Clemmensen reduction reaction. 

3-Oxobutanoic acid (also known as acetoacetic acid) undergoes Clemmensen reduction to form butanoic acid.

Clemmensen reduction involves the reduction of carbonyl compounds (aldehydes or ketones) using zinc amalgam (Zn/Hg) in the presence of **hydrochloric acid (HCl). It reduces the carbonyl group (C=O) of aldehydes and ketones to a methylene group (CH_2)

Reaction of 3-Oxobutanoic Acid: In the case of 3-oxobutanoic acid, the carbonyl group in the ketone position (\(\text{-CO-}\)) is reduced to a methylene group \(\text{-CH_2-}\), while the carboxylic acid group (\(\text{-COOH}\)) remains unaffected under Clemmensen conditions.

The reaction can be represented as:

Thus, the product of the Clemmensen reduction of 3-oxobutanoic acid is butanoic acid.

Mechanism :