Two identical satellites are moving around the earth in circular orbits at heights $3R$ and $R$ respectively where $R$ is the radius of the Earth. The ratio of their kinetic energies is 

• A

  $2\mathrm{ }:\mathrm{ }1$
• Correct answer
  B

  $1 : 2$
• C

  $3 : 1$
• D

  $2 : 3$

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