$A$ - $80\%$ of total global carbon is dissolved in the oceans.
$R$ - The dry weight of organisms consists of $49\%$ carbon.

• 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.