Which ground state E.C. of a transition element does not exist?

Which of the following transition elements does not exhibit variable oxidation states ?

Transition metals show variable oxidation states due to tendency of ‘d’ as well as ‘s’ electrons to take part In bond formation:- Which element in the first series of transition elements does not exhibit variable oxidation states and why?

The common oxidation state of transition elements is

Though Sc is a transition element, it does not exhibit variable oxidation state. Why ?

Which transition element does not exhibit variable oxidation state?

Which transition element does not exhibit variable oxidation state?

Which one of the following group 16 element does not exist in -2 oxidation state?