$\begin{array}{1 1} (A) \overrightarrow b\; is \;collinear \;vector. \\ (B) \overrightarrow b\; is \;unit \;vector. \\ (C) \overrightarrow a\; and \;\overrightarrow b\;are \;equal\; vectors. \\ (D) \overrightarrow b is\; any\; vector. \end{array} $