All transition elements are d-block elements, but all d-block elements can not be transitional. This exceptional behaviour is shown by ____ group elements

II B group elements are d-block but not transition elements.

Those elements which either themselves or their ions have incompletely filled d-orbitals are called transition elements. They are all d-block elements because ‘d’ orbitals are progressively filled.
But those d-block elements or their ions which do not have incompletely filled d-orbitals are not transition elements, e.g., Zn, Cd and Hg are d-block elements but not transition metals.