If the sum of the circumferences of two circles with radii $R_{1}$ and $R_{2}$ is equal to the circumference of a circle of radius $R$,then

• A
  $R_{1} + R_{2} < R$
• B
  $R_{1} + R_{2} > R$
• C
  Nothing definite can be said about the relation among $R_{1}, R_{2}$ and $R$
• D
  $R_{1} + R_{2} = R$