A, B, and C are hydroxy-compounds of the elements X, Y, and Z respectively. X, Y, and Z are in the same period of the periodic table. A gives an aqueous solution of pH less than seven. B reacts with both strong acids and strong alkalis. C gives a strongly alkaline aqueous solution. Which of the following statements is/are true? I: The three elements are metals. II: The electronegativities decrease from X to Y to Z. III: The atomic radius decreases in the order X, Y, and Z. IV: X, Y, and Z could be phosphorus, aluminum, and sodium respectively.