Consider the following chemical transformation: 4-oxocyclohexanecarboxylic acid X 4-hydroxycyclohexanecarboxylic acid The most suitable reagent 'X' for this conversion is:

Step-by-step solution

In the given transformation, the ketone group is reduced to a secondary alcohol, while the carboxylic acid group remains unaffected. NaBH ₄ is a mild reducing agent that chemoselectively reduces aldehydes and ketones to alcohols but does not reduce carboxylic acids or esters. LiAlH ₄ is a strong reducing agent and would reduce both the ketone and the carboxylic acid groups. B ₂ H ₆ is an excellent reagent for the reduction of carboxylic acids. Zn(Hg) / HCl (Clemmensen reduction) would reduce the ketone group to a m