Answer 1

 Transition elements (with reference to variability of oxidation states)
- The transition elements shows variable oxidation states - due to incomplete filling of d
- orbitals in such a way that their oxidation states differ from each other by unity. 

eg `V^{II},V^{III},V^{IV},V^V 
p - block elements (with reference to variability of oxidation states) 
- In p - block elements, we have a group oxidation state (which is sum of ns electrons and np electrons)
- down the group, the group oxidation no. decreasess by (+2) unit, due to inert pair effect.