Answer is (b) $-11$

It is given that $x=3$ is a solution of $3 x^{2}+(k-1) x+9=0$;
therefore, we have:

$\begin{array}{l}
3(3)^{2}+(k-1) \times 3+9=0 \\
\Rightarrow 27+3(k-1)+9=0 \\
\Rightarrow 3(k-1)=-36 \\
\Rightarrow(k-1)=-12 \\
\Rightarrow k=-11
\end{array}$