Answer
Points $a$ and $b$ are moving upward.
Points $c$ and $d$ are moving downward.
Points $e$ and $f$ are moving downward.
Points $g$ and $h$ are moving upward.
Work Step by Step
Since the wave is moving in the positive direction, a peak is approaching points $a$ and $b$. Thus points $a$ and $b$ are moving upward. A trough is approaching points $c$ and $d$. Thus points $c$ and $d$ are moving downward.
As time increases, points $e$ and $f$ move towards a trough so points $e$ and $f$ are moving downward. Points $g$ and $h$ move towards a peak so points $g$ and $h$ are moving downward.
