$\operatorname{coth}^2 x-\tanh ^2 x=$

• A

  $4 \operatorname{cosech} 2 x \tanh 2 x$
• B

  $4 \operatorname{sech} 2 x \operatorname{coth} 2 x$
• C

  $4 \operatorname{sech} 2 x \tanh 2 x$
• Correct answer
  D

  $4 \cosh 2 x(\operatorname{cosech} 2 x)^2$

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