The correct order of acid strength is :

The acid strength of the given oxoacids can be determined by considering the number of oxygen atoms and the electronegativity of the central atom (in this case, chlorine). Generally, as the number of oxygen atoms increases, the acid strength also increases due to the greater ability to stabilize the negative charge on the conjugate base. The correct order of acid strength is based on the stability of the conjugate base and the electronegativity of the central atom. The more oxygen atoms attached to the central chlorine atom, the more stable the conjugate base will be, thus making the acid stronger. Therefore, the correct order from weakest to strongest acid is: HClO < HClO2 < HClO3 < HClO4. This matches option (A). Think of it this way: the acid strength increases with the number of oxygen atoms because the additional oxygen atoms help to disperse the negative charge on the conjugate base, making it more stable.