Question:
Out of the given matrices, choose that matrix which is a scalar matrix:
(a) $\left[\begin{array}{ll}0 & 0 \\ 0 & 0\end{array}\right]$
(b) $\left[\begin{array}{lll}0 & 0 & 0 \\ 0 & 0 & 0\end{array}\right]$
(c) $\left[\begin{array}{ll}0 & 0 \\ 0 & 0 \\ 0 & 0\end{array}\right]$
(d) $\left[\begin{array}{l}0 \\ 0 \\ 0\end{array}\right]$
Solution:
(a) $\left[\begin{array}{ll}0 & 0 \\ 0 & 0\end{array}\right]$
A diagonal matrix in which all the diagonal elements are equal is called the scalar matrix.