1. The problem asks which graph represents the relation $y = -x$. 2. The equation $y = -x$ is a linear function where the slope is $-1$ and the y-intercept is $0$. 3. This means the graph is a straight line passing through the origin $(0,0)$ with a downward slope. 4. For every increase of $1$ in $x$, $y$ decreases by $1$. 5. The line will pass through points like $(1,-1)$, $(2,-2)$, and $(-1,1)$. 6. The graph is symmetric about the origin and forms a 45-degree angle with the negative x-axis and positive y-axis. 7. Therefore, the graph representing $y = -x$ is a straight line through the origin with slope $-1$.