Which Is the Most Likely Regulated Step in Metabolic Pathways

Which is the most likely regulated step in metabolic pathways?

A) The first reaction in the pathway, regardless of whether it is reversible or irreversible.
B) The first irreversible reaction of the pathway.
C) The first endergonic reaction in the pathway.
D) The last reaction of the pathway.
E) The reaction whose enzyme is present in the highest activity in the cell.