Bean Plants Significantly Change the Development of Their Roots When

Bean plants significantly change the development of their roots when they make nodules,as well as diverting energy and resources for this change.Given the critical role of normal roots,why would the plant make this change?

A) because Rhizobium produces ammonium (NH₄⁺)
B) because Rhizobium produces nitrogen (N₂)
C) because Rhizobium produces sugars
D) because Rhizobium protects the plants from predators
E) because Rhizobium protects the plants from parasites