The correct statement regarding chromate and dichromate is

• A

  The oxidation states of chromium in chromate and dichromate are, respectively, +4 and +6
• B

  Dichromate on reaction with concentrated $\mathrm{H}_2 \mathrm{SO}_4$ gives chromate
• C

  All chromium-oxygen bond distances in dichromate are equal
• Correct answer
  D

  Total number of electrons involved in the complete reduction of one molecule of dichromate to chromium(III) is six

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