80. The scheme describes the catalytic hydrogenation pathway of 1-butene to butane. Which of the following statements belowcorrectly shows the steps?   
(A) (X)-oxidative addition, (Y)-reductive elimination, (Z)- ligand association
(B) (X)-ligand association, (Y)-reductive elimination, (Z)-oxidative addition
(C) (X)-reductive elimination, (Y)- oxidative addition, (Z)-ligand association
(D) (X)-reductive elimination, (Y)-ligand association, (Z)-oxidative addition
(E) (X)- ligand association, (Y)- oxidative addition, (Z)-reductive elimination