If two planes intersect, then they intersect in exactly one point. true or false?

False

A plane is a flat line that extends forever in all directions. Think of a flat piece of paper that does not bend or curve. If you intersect two planes, then they will form a straight line. This line will extend forever both directions. There are infinitely many points on this line of intersection. You can think of a book as a good example: the pages are the planes while the spine is the line of intersection.