The strongest acid amongst the following compounds is

– I effect exerting (electron withdrawing) groups increases the acidic strength of an acid by withdrawing electron density towards itself, they weaken O – H bond and thus, the release of H+ ion by an acid becomes easier. Whereas + I effect exerting (e- releasing) groups decreases the acidic strength by donating electron density to O-atom. Further, – I effect decreases with distance. Thus, the acidic strength of the given acids would bestrongest acid than other given compounds.