bec first........... they show variable valancies

second.........s block consists of pure metals p block consists of almost non metals but d block elements have intermediate prop of both or in other words they are a transient phase in which the prop change from metallic to non metallic.................so they are called transition elements

D - BLOCK ELEMENT ARE CALLED TRASITION ELEMENTS BCOZ THY SHOW TRANSITION FRM METAL TO NON-METAL PROPERTY......

THY ALSO HAVE VARIALBLE VALENCY.......DUE TO THS THEY POSSES BOTH METALLIC AND NON METALLIC PROPERTY.........