Answer
$$HCl \gt HF \gt HClO \gt HC_6H_5O$$
Work Step by Step
Since all solutions have the same concentration, the $[H_3O^+]$ is proportional to the strength of each acid. Thus, the strongest acid will have the greater hydronium ion concentration.
Since $HCl$ is the only strong acid in this sequence, it is the strongest acid.
The other acids can be ranked by their strengths using their $K_a$ values (See Table 16.5).
$$HF \gt HClO \gt HC_6H_5O$$
