If $\cosh 2 x=199$, then $\operatorname{coth} x=$

• A

  $\frac{5}{3 \sqrt{11}}$
• B

  $\frac{5}{6 \sqrt{11}}$
• C

  $\frac{7}{3 \sqrt{11}}$
• Correct answer
  D

  $\frac{10}{3 \sqrt{11}}$

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