Ferric chloride is applied to stop bleeding from a cut because:

• A
  $Fe^{3+}$ ion coagulates blood,which is a negatively charged sol
• B
  $Fe^{3+}$ ion coagulates blood,which is a positively charged sol
• C
  $Cl^{-}$ ion coagulates blood,which is a positively charged sol
• D
  $Cl^{-}$ ion coagulates blood,which is a negatively charged sol