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 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.