下列矩阵中，不是初等矩阵的是
A. $\left(\begin{array}{lll}0 & 1 & 0 \\ 1 & 0 & 0 \\ 0 & 0 & 1\end{array}\right)$
B. $\left(\begin{array}{lll}1 & 0 & 0 \\ 0 & 3 & 0 \\ 0 & 0 & 1\end{array}\right)$
C. $\left(\begin{array}{lll}1 & 0 & 0 \\ 2 & 1 & 0 \\ 0 & 0 & 1\end{array}\right)$
D. $\left(\begin{array}{lll}1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 0\end{array}\right)$