3.（5.9分）若已知A是分块矩阵，即A=}A_(1)& & & A_(2)& & &ddots O& & A_(7)

3.（5.9分）若已知A是分块矩阵，即 $A=\begin{bmatrix}A_{1}& & \\& A_{2}& \\& &\ddots \\O& & A_{7}\end{bmatrix}$,则$\lambda A=（）$

A. $\begin{bmatrix}\lambda A_{1}& & \\& \lambda A_{2}& \\& &\ddots \\O& & \lambda A_{7}\end{bmatrix}$

B. $\begin{bmatrix}O& & \\& \ddots \\A_{1}&\end{bmatrix}$

C. $\begin{bmatrix}O& & \\&\ddots \\&\lambda A_{2}\end{bmatrix}$