$l=\lim _{\theta \rightarrow 0}\left(\frac{3 \sin \theta-4 \sin ^3 \theta}{\theta}\right)$ and $m=\lim _{\theta \rightarrow 0}\left(\frac{2 \tan \theta}{\theta\left(1-\tan ^2 \theta\right)}\right)$ is

• A

  $x^2+5 x+6=0$
• Correct answer
  B

  $x^2-5 x+6=0$
• C

  $x^2-5 x-6=0$
• D

  $x^2+5 x-6=0$

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