please work out the solution step by step

For a given matrix A=[3113], the matrix P that is orthogonally diagonalizes A is of the following matrices are diagonalizable. I) P=[21212121], II) P=[0110] III) P=[21212121] (1) only (I) is true (2) only (II) is true (3) only (III) is true (4) None of the given answers is true