In a triangle ABC if the angles $\mathrm{A}, \mathrm{B}, \mathrm{C}$ are in AP , then which one of the following is correct?

• A

  $c=a+b$
• B

  $c^2=a^2+b^2-a b$
• C

  $a^2=b^2+c^2-b c$
• Correct answer
  D

  $b^2=a^2+c^2-a c$

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