In order to help the police ，the witness described what he had seen very carefully not to ______ any detail.

A．act out

B．leave out

C．pick out

D．put out

若n阶矩阵A=(α₁，α₂，…，α_n-1，α_n)的前n-1个列向量线性相关，后n-1个列向量线性无关，β=α₁+α₂+…+α_n，证明：

方程组AX=β必有无穷多解；