In context with the transition elements, which of the following statements is incorrect ?
A. In the highest oxidation states, the transition metal show basic character and form cationic complexes.
B. In the highest oxidation states of the first five transition elements (Sc to Mn), al the 4 s and 3d electrons are used for bonding.
C. Once the `d^(5)` configuration is exceeded, the tendency to involve all the 3d electrons in bonding decreases.
D. In addition to the normal oxidation states, the zero oxidation state is also shown by these elements in complexes.