D - block elements are very useful as catalysts – True or False?

The correct option is A True
The transition metals and their compounds are widely used as catalysts. This is because of the high charge to volume ratio of their ions and the availability of low-energy free orbitals for bond formation. In other words, transition elements tend to adopt multiple oxidation states and form complexes readily. For example, in the contact process for the manufacture of Sulphuric acid - divanadium pentoxide is used as a catalyst to convert $S{O}_2$ into $S{O}_3$. Likewise, in the Haber process, Iron is used to improve the yield of ammonia.