The correct option is A NO2CH2COOH > NCCH2COOH > FCH2COOH > ClCH2COOH
Acidic strength increases as the stability of the conjugate base increases.
Considering the strength of the given electron withdrawing group in the acids, acidic strength follows the order:
NO2CH2COOH > NCCH2COOH > FCH2COOH > ClCH2COOH