A man is walking towards a vertical pillar in a straight path, at a uniform speed. At a certain point $A$ on the path, he observes that the angle of elevation of the top of the pillar is ${30}^{°}$.  After walking for $10$ minutes from $A$ in the same direction, at a point $B$, he observes that the angle of elevation of the top of the pillar is ${60}^{°}$ . Then the time taken (in minutes) by him, from $B$ to reach the pillar, is

• A

  $20$
• Correct answer
  B

  $5$
• C

  $6$
• D

  $10$

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