An explosion releasing energy E occurs in a medium of density $\rho$. This results in a spherical blast wave of radius $r$. One can express the radius of the blast wave at time $t$ after the explosion in a form $r=k t^\alpha E^\beta \rho^\gamma$ where $k$ is a dimensionless constant. Then the radial speed of the blast wave can be written as $v \propto t^n$. The value of $n$ is

• A

  $-3$
• B

  $1 / 5$
• Correct answer
  C

  $-3 / 5$
• D

  $2$

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