Which one of the following on reduction with NaBH4 gives an equimolar mixture of sorbitol and mannitol?

Fructose

The correct answer is option 4. fructose.

Fructose is a six-carbon sugar with a ketone group. When it is reduced with \(NaBH_4\), it forms an equimolar mixture of sorbitol and mannitol. Sorbitol is a polyhydroxy alcohol with six carbons, and mannitol is a polyhydroxy alcohol with five carbons.

The other answer choices, mannose, glucose, and xylose, are all six-carbon sugars with an aldehyde group. When they are reduced with \(NaBH_4\), they form only sorbitol.