Problem : What must be true of a surface in order for it to be a simple closed surface?
Problem : If a line is perpendicular to a plane, is that line perpendicular to every line in the plane?
Problem : If a polyhedron has 6 faces, how many edges does it have?
Problem : Is a surface two-dimensional or three-dimensional?
Problem : Is it possible for a surface to be contained in a single curve?