The half-life period of a radioactive element $x$ is the same as the mean life time of another radioactive element $y$. Initially,they have the same number of atoms. Then:

• A
  $x$ will decay faster than $y$.
• B
  $y$ will decay faster than $x$.
• C
  $x$ and $y$ have the same decay rate initially and later on different decay rates.
• D
  $x$ and $y$ decay at the same rate always.