Which of the following systems have a unique solution?
(a) $\left(\begin{array}{rr}3 & 1 \\ -1 & -1 \\ 2 & 0\end{array}\right)\left(\begin{array}{l}x \\ y\end{array}\right)=\left(\begin{array}{l}0 \\ 2 \\ 2\end{array}\right)$,
(b) $\left(\begin{array}{rrr}1 & 2 & -1 \\ -2 & 3 & 0\end{array}\right)\left(\begin{array}{l}x \\ y \\ z\end{array}\right)=\left(\begin{array}{l}1 \\ 2\end{array}\right)$.
(c) $\left(\begin{array}{rrr}2 & 1 & -1 \\ 0 & -3 & -3 \\ 2 & 0 & -2\end{array}\right)\left(\begin{array}{c}u \\ v \\ w\end{array}\right)=\left(\begin{array}{r}3 \\ -1 \\ 5\end{array}\right)$,
(d) $\left(\begin{array}{lll}1 & 4 & -1 \\ 1 & 3 & -3 \\ 2 & 3 & -2\end{array}\right)\left(\begin{array}{l}u \\ v \\ w\end{array}\right)=\left(\begin{array}{r}-2 \\ -1 \\ 1\end{array}\right)$.