I interpret this as the logical conjunction of two statements. That is, if A and B are statements the logical conjunction is that both are true. The statements A and B can each be represented by a circle. Where the circles overlap is their logical conjunction. We can call this overlap C. C contains only those elements where both A and B are true. The interlocking region is closed. Example, A is the set of all red objects and B is the set of all spherical objects. C is the set of all red spherical objects. The opposite of a closed set is an open set. In the example, this would be everything other than red spherical objects. So TRUE.