Transition elements belongs to which of the following block?

d-block

Transition elements belongs to d block.

The transition elements are those elements which either in their elemental state or in their commonly occurring oxidation states have partially filled d-subshell. This definition includes coinage metals (Cu, Ag, Au) in the transition elements as their ions have partially filled (n-1)d subshell although their atoms have filled (n-1)d subshell in the ground state.