$[\mathrm{x}]$ represents the greatest integer function. If $\lim _{x \rightarrow 0^{+}} \frac{\cos [x]-\cos (k x-[x])}{x^2}=5$ then $k=$

• Correct answer
  A

  $\sqrt{10}$
• B

  $\sqrt{11}$
• C

  $3$
• D

  $9$

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