Which term best represents the intersection of two pages of an open book?

plane

point

line

angle

The correct answer is line. That's because it is made out of an infinite number of small points where they meet and you can connect them all. A page itself would be a plane, while a point would be anything along the line or anything on the plane itself. The angle would be the angle at which two pages meet, that is, two planes, but the intersection itself is a line.