I have just started the textbook Geometry: its elements and structure by Alfred Posamentier.
The first set of questions refers to the following diagram:
The very first question is "What is the intersection of $\overline{AB}$ and $\overline{CD}$?" If an intersection is defined as the set of all elements that are common to two sets. Then I think the answer should be an empty set since $\overline{AB}$ contains no elements in common with $\overline{CD}$. However, the solutions manual lists the answer as $\overline{CB}$. Where am I going wrong?