d
(d) Matrix $\left[ {\begin{array}{*{20}{c}}1&2&3\\4&5&6\\3&\lambda &5\end{array}} \right]$ be non singular,
only if $\left| {\,\begin{array}{*{20}{c}}1&2&3\\4&5&6\\3&\lambda &5\end{array}\,} \right| \ne 0$
==> $\,1(25 - 6\lambda ) - 2(20 - 18) + 3(4\lambda - 15) \ne 0$
==> $25 - 6\lambda - 4 + 12\lambda - 45 \ne 0$
==> $6\lambda - 24 \ne 0$==> $\lambda \ne 4$.