Condition under which vectors (a + b) and (a $\mathbf{-}$ b) are parallel is

• A

  $\mathbf{a}\mathbf{\perp }\mathbf{b}$

• B

  $\left|\mathbf{a}\right| = \left|\mathbf{b}\right|$

• C

  $\mathbf{a}\mathbf{\ne }\mathbf{b}$

• D

  a is parallel to b