Ans: A
Note that the slope of $L$
Note that the slope of $L$
$\begin{array}{cl}
= & \tan(180^\circ- 45^\circ) \\
= & -1
\end{array}$
Therefore, the equation of $L$ is
$\begin{array}{rcl}
y-0 & = & (-1)(x-4) \\
x + y & = & 4
\end{array}$
