Correct Option: A

Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C2O42–), is a chelating agent for metal cations. Oxalic acid's main applications include cleaning or bleaching, especially for the removal of rust, e.g. Bar Keepers Friend is an example of a household cleaner containing oxalic acid. Its utility in rust removal agents is due to its forming a stable, water soluble salt with ferric iron, ferrioxalate ion.