Through a given point on a line, there is one and only one line perpendicular to the given line.
The hints that it gave was "Do not limit your thinking to just two dimensions". If it just a regular line there will only be one perpendicular line right?
hold a pencil up. A real pencil. I bet you can make perpendiculars in many directions, because the pencil is in a three dimensional space.
I don't get what you mean by holding up a pencil. I hold up one and I don't see anything?