In a triangle $A B C$, if $a, b, c$ are in arithmetic progression and the angle $A$ is twice the angle C, then $\cos \mathrm{A}: \cos \mathrm{B}: \cos \mathrm{C}=$

• A

  $2: 3: 4$
• B

  $3: 4: 8$
• Correct answer
  C

  $2: 9: 12$
• D

  $1: 9: 6$

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