Provide an Appropriate Response $\left[\begin{array}{ccc}\frac{1}{2} & \frac{1}{2} & 0 \\ 0 & 0 & 1\end{array}\right]$

Essay

Provide an appropriate response.
-In the context of Markov chains, explain why the matrix below could not be a transition matrix.
$\left[\begin{array}{ccc}\frac{1}{2} & \frac{1}{2} & 0 \\ 0 & 0 & 1\end{array}\right]$