$A-$ The microbe $Frankia$ produces nitrogen-fixing nodules on the roots of non-leguminous plants.
$R-$ Both $Rhizobium$ and $Frankia$ are free-living in soil,but as symbionts,can fix atmospheric nitrogen.

• A
  $A$ and $R$ both are correct.
• B
  $A$ and $R$ both are incorrect.
• C
  $A$ is correct,$R$ is incorrect.
• D
  $A$ is incorrect,$R$ is correct.