#### Answer

(a) is increasing on the interval $(0, +\infty)$
(b) has no interval where it is decreasing
(c) has no interval where it is constant

#### Work Step by Step

Based on its graph, the given function:
(a) is increasing on the interval $(0, +\infty)$
(b) has no interval where the function is decreasing
(c) has no interval where it is constant