In this question, we have to define the order of acid strength among the options, and there are a few ways to determine the strength of an acid, some of these are Ka, pKa and the percent of ionization (or dissociation).
For Ka, the higher the value, the more the acid is dissociating in a solution, and acid strength is all about dissociation capacity, if the acid can dissociate 100%, this means that the acid is really strong
For pKa is the opposite, a lower pKa indicates a stronger acid
Therefore based on these informations we have that the stronger acid will of course be the 100% dissociated, as I have explained, strength of acids is all about dissociation
The order will be:
IV
III
II
I
Letter A