Answer
Figure (I) is the graph of $y(t)$.
Figure (II) is the graph of $x(t)$.
Work Step by Step
From Figure 17 (A) we see that as $x$ increases, $y$ decreases and passes 0 to reach the minimum point and then increases. So, Figure (I) is the graph of $y(t)$. Also from Figure 17 (A) $x$ increases, decreases and then increases. So, Figure (II) is the graph of $x(t)$.