设向量组 $\alpha_{1},\alpha_{2},\alpha_{3}$ 线性无关，则下列向量组线性相关的是( ) (A) $\alpha_{1} - \alpha_{2}, \alpha_{2} - \alpha_{3}, \alpha_{3} - \alpha_{1}$ . (B) $\pmb{\alpha}_{1} + \pmb{\alpha}_{2}, \pmb{\alpha}_{2} + \pmb{\alpha}_{3}, \pmb{\alpha}_{3} + \pmb{\alpha}_{1}$ . (C) $\alpha_{1} - 2\alpha_{2}, \alpha_{2} - 2\alpha_{3}, \alpha_{3} - 2\alpha_{1}$ . (D) $\pmb{\alpha}_{1} + 2\pmb{\alpha}_{2}, \pmb{\alpha}_{2} + 2\pmb{\alpha}_{3}, \pmb{\alpha}_{3} + 2\pmb{\alpha}_{1}$ .