Q. Most transition metals
I. form sets of compounds which display different oxidation states of the metal
II. form coloured ions in solution
III. burn vigorously in oxygen
IV. replace from dilute acids of these.

 2506  167 The d-and f-Block Elements Report Error

Solution:

I. True, due to involvement of ns-electrons in bonding.
II. True, due to unpaired electrons in d-orbitals.
III. Since,
Thus oxidation of the metal is not easy. Thus, false.
IV. They do not displace with dilute acid based on values. Thus false. Thus I and II are true.