$Assertion$ : The number of significant figures depends on the least count of the measuring instrument.
$Reason$ : Significant figures define the accuracy of the measuring instrument.

• A
  If both $Assertion$ and $Reason$ are correct and the $Reason$ is a correct explanation of the $Assertion$.
• B
  If the $Assertion$ is correct but $Reason$ is incorrect.
• C
  If both $Assertion$ and $Reason$ are correct but $Reason$ is not a correct explanation of the $Assertion$.
• D
  If both the $Assertion$ and $Reason$ are incorrect.