(i) The lowest oxide of a transition metal is basic because the metal is in a lower oxidation state with more metallic character. For example, MnO is basic as manganese is in +2 oxidation state. The highest oxide is amphoteric or acidic because the metal is in a high oxidation state with high charge density. For example, Mn₂O₇ is acidic as manganese is in +7 oxidation state. In lower oxidation states, the metal can donate electrons easily, making the oxide basic. In higher oxidation states, the metal can accept electrons, making the oxide acidic.

(ii) Transition metals exhibit their highest oxidation state in oxides and fluorides because oxygen and fluorine are highly electronegative elements. They can stabilize high oxidation states by accepting electrons from the metal. Both oxygen and fluorine are small in size and can form strong bonds with the metal, which helps in stabilizing the high oxidation state.

(iii) The highest oxidation state of a metal is exhibited in oxoanions because the metal forms multiple bonds with oxygen in these ions. For example, in permanganate ion (MnO₄⁻), manganese exhibits +7 oxidation state, and in dichromate ion (Cr₂O₇²⁻), chromium exhibits +6 oxidation state. The formation of multiple bonds with oxygen helps stabilize these high oxidation states.