\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
What is the size of the following matrix?$$\mathbf{D}=\begin{pmatrix}1&0&0 \\ 0&1&0 \\ 0&0&1 \end{pmatrix}$$
Size:
\(\times\)