Which one will act as a strong acid?

Explanation

Chloro groups cause an inductive effect(-I). i.e it is a withdrawing group because it is more electronegative than carbon to which it is attached. -Cl groups pull the bonded electrons from carbon and carbon in turn pulls the electron pair from hydrogen of -COOH group causing more electron deficiency on hydrogen. hydrogen becomes more partially positive hence more acidic. greater the withdrawing effect greater will be polarity and acidity. Since trichloro substituted acetic acid has greater no. of withdrawing groups (3 chloro groups)so it will be more polar and more acidic.