In which of the following the former acid is stronger the later oneI)  CF3COOH, HCOOH II) Cl2CHCOOH,FCH2COOH   III) C6H5COOH,CH3COOH

I) Due to tri-fluoro-acetic acid causes more – I effect than  HCOOHII) Presence of two chlorine atoms causes more – I effect than one –F atom.III) Phenyl group is EWG (-I group) while −CH3  group is EDG (+I group)