$A$ $LASER$ is a source of very intense,monochromatic,and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source of light. $A$ laser light beamed at the Moon takes $2.56 \; s$ to return after reflection at the Moon's surface. How much is the radius of the lunar orbit around the Earth?

• A
  $3.84 \times 10^{7} \; km$
• B
  $3.84 \times 10^{5} \; km$
• C
  $7.16 \times 10^{6} \; km$
• D
  $3.84 \times 10^{7} \; m$