Exercise 16 Page 384

Opposite rays always share the same endpoint. For us to find two rays that are not opposite, it is enough to find two rays that do not share endpoints. For our first ray we can arbitrarily choose $\overrightarrow{AC}.$

Let's now name any ray with an endpoint other than $A\text{,}$ such as $\overrightarrow{ED}.$

The two rays $\overrightarrow{AC}$ and $\overrightarrow{ED}$ are not opposite. This is just an example solution, so feel free to choose a different pair of rays which do not have the same endpoint!