The Ka values of HCI, CH3COOH, HF, and H2SO4 are 107, 1.85 x 10^-5, 6.7 x 10^-5 and 102 respectively. The decreasing order of acidic strength is:

Explanation

Ka is a measure of ionization of the acid, thereby a greater Ka corresponds to greater acidic strength. The question asks for DECREASING order of acidic strength so, the acids are to be listed from strongest to weakest. HCl is the strongest with the greatest Ka (107), followed by H2SO4 (102), followed by HF (6.7 x 10-5), and then CH3COOH which is the weakest having the lowest Ka (1.85 x 10-5). Option B has this correctly laid out so, it is the answer. Option A has the order in reverse, as it lists the acid down in increasing order of acidic strength. Options, C and D, have them listed incorrectly, as C has CH3COOH before the rest while D has HF mentioned before H2SO4.