Which of the following hexoses will form the same osazone when treated with excess phenyl hydrazine?

• A

  D-glucose, D-fructose and D-galactose
• Correct answer
  B

  D-glucose, D-fructose and D-mannose
• C

  D-glucose, D-mannose and D-galactose
• D

  D-fructose, D-mannose and D-galactose

Solution

D-glucose, D-fructose and D-mannose form the same osazone when treated with excess of phenyl hydrazine because they differ only in Ist and 2nd carbon atoms which are transformed to the same form.
They form the following osazone

Hence, the correct answer is option: 'B'.