The concentration of the given solutions can be calculated in terms of molarity. Molarity is given by the formula

For option (i) Molarity of NaOH = = 2.5M

(ii) Molarity of KCl = 0.5/0.2 = 2.5M

(iii) Molarity of NaOH = = 10M

(iv) Molarity of KOH = = 1.7M

The solutions (i) and (ii) have the same concentration.