A, B and C are hydroxyl 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 $p^H$  less than seven. B reacts with both strong acids and strong alkalies. C gives an aqueous solution which is strongly alkaline.
Which of the following statements is/are true?
I: The three elements are metals 
II: The electronegativities decreases 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, aluminium and sodium respectively.