b
$\vec{E}=-\left[\frac{\partial V}{\partial x} \hat{i}+\frac{\partial V}{\partial y} \hat{j}+\frac{\partial V}{\partial z} \hat{k}\right]$
Here, $\frac{\partial V}{\partial x}=\frac{\partial}{\partial x}(2 x+3 y-z)=2$
$\frac{\partial V}{\partial y}=\frac{\partial}{\partial y}(2 x+3 y-z)=3$
$\frac{\partial V}{\partial z}=\frac{\partial}{\partial z}(2 x+3 y-z)=-1$
$\therefore \vec{E}=-2 \hat{i}-3 \hat{j}+\hat{k}$