In a Venn diagram, a triangle represents photographers, a circle represents fashion photography, a hexagon represents sports photography, a rectangle represents editorial photography, and a square represents wildlife photography. If the letter 'C' lies exactly in the intersection of the triangle, circle, and square only, what does 'C' represent?

In a survey of a class represented by a Venn diagram, there are three intersecting circles representing students who know English, Spanish, and French. The region representing students who know both Spanish and French contains the number 20. Which number represents the group of students knowing both Spanish and French?

Which of the following logical groups is best represented by a Venn diagram consisting of three mutually intersecting circles where some members can be common to any two or all three groups?