0.2 molar solution of formic acid is ionized 3.2%. Its ionization constantis[MP PMT 1991]

• A. \[1\times {{10}^{-12}}\]
• B. \[2.1\times {{10}^{-4}}\]
• C. \[1.25\times {{10}^{-6}}\]
• D. \[1\times {{10}^{-14}}\]