#### Answer

$a.$ $C,D$
$b.$ $A,B,E$
$c.$ $A,B,E,D,C$

#### 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 $A,B,E,D,C$.