$a.$ $C,D$ $b.$ $A,B,E$ $c.$ $A,B,E,D,C$
Work Step by Step
$a.$ The slope is negative at the points where the function is decreasing which is at $C$ and $D$. $b.$ The slope of the curve is positive when the function is increasing which is at $A$, $B$, $E$. $c.$ We will have to list the points from the steepest upward slope to the steepest downwards slope which is $A,B,E,D,C$.