The `d-`block elements easily form alloys because-

Options

A. Their `d-`block are only partly filled
B. They have very widely differing atomic sizes.
C. They are very similar in their atomic sizes
D. They are highly electronegative in character

Explanation

In the case of the transition metals the atomic radii have values which are very close, that is they are of very similar size. Hence the atom of an element in a crystal lattice can easily be replaced by a metal atom of another transition elements. This makes metals form alloys very easily.