3. Incorrect. The answer is true not false. A ∩ B means the intersection of sets A and B. This new set contains all elements which belong to both A and B. Looking at the periodic table for transition elements (A has a blue border and B is highlighted in yellow.), it is easy to see that Cu is in both sets.
If there were no intersection, both sets would not have elements in common. In that case, both sets would be called 'disjoint' sets. The intersection of both sets gives an empty set (Ř). Graphically, the Venn diagram is: