Let R and S be equivalent on set A, then the symmetry (A) of RUS is still symmetric because of the symmetric set.

A must be true, B must not be true, and C may not be true.

Let A and B be compatible relations on the set A, then the following are incompatible relations: (c) Strictly speaking, they should intersect and are not necessarily compatible.

Answer a.a c ∪ b c

Compatibility: reflexivity and symmetry

How to calculate the ∩∩ between relationships?

When the relationship is represented by a set of binary combinations, it is enough to find the union and intersection.