Answer
Graph (b).
Work Step by Step
We need to find the anti-derivative for $\dfrac{dy}{dx}=-x$
Thus, we have $y=-\dfrac{x^2}{2}+C$
Plug in $x=1,y=1$ into the above equation to solve for $C$.
we get $C=\dfrac{3}{2}$
Thus, $y=-\dfrac{x^2}{2}+\dfrac{3}{2}$; which shows graph (b) with a concave-down parabola.