In a $\triangle A B C, \frac{2\left(r_1+r_3\right)}{a c(1+\cos B)}=$

• A

  $\frac{\Delta}{\mathrm{b}}$
• Correct answer
  B

  $\frac{\mathrm{b}}{\Delta}$
• C

  $\frac{2 \Delta}{a+b+c}$
• D

  $\frac{a+b+c}{2 \Delta}$

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