# Please explain why part (c) of this question is False?

If the row reduced echelon form of matrix $M$ is $R = \mathbb{I}$, then $M$ is invertible and $M \boldsymbol{x} = \boldsymbol{b}$ has one solution: $\boldsymbol{x} = {M}^{- 1} \boldsymbol{b}$