Consider the following two statements $A$ and $B$ and identify the correct choice in the given answer.
$A:$ The characteristic $X-$ray spectrum depends on the nature of the material of the target.
$B:$ The short wavelength limit of the continuous $X-$ray spectrum varies inversely with the potential difference applied to the $X-$ray tube.

• A
  $A$ is true and $B$ is false.
• B
  $A$ is false and $B$ is true.
• C
  Both $A$ and $B$ are true.
• D
  Both $A$ and $B$ are false.