Which of the following sets are equal? (i) A = {1, 2, 3} (ii) B= {x∈R : x^2 -2x +1 = 0} (iii) C = {1, 2, 2, 3} (iv) D= {x∈R : x^3 – 6x^2 + 11x – 6 = 0}.