Which of the following property is not the characteristic of transition elements?

Natural radioactivity

Characteristics of transition elements:

(i) All the transition elements are metals and they form variable oxidation states.

(ii) Transition metals forms a large number of complex compounds.

(iii) Transition metals or their compounds are coloured and is mainly due to:

      (a) d-d transitions

      (b) charge transfer spectra

      (c) polarisation