In Young's double slit experiment, if the distance between $5^{\text {th }}$ bright and $7^{\text {th }}$ dark fringes is 3 mm, then the distance between $5^{\text {th }}$ dark and $7^{\text {th }}$ bright fringes is

• A

  6 mm
• B

  3 mm
• Correct answer
  C

  5 mm
• D

  4 mm

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