When two D.C. generators are running in parallel an equilizer bar is used______________?

When two D.C. generators are running in parallel an equilizer bar is used______________?

A. to increase the series flux
B. to increase the generated e.m.f.
C. to reduce the combined effect of ar-mature reaction of both the machines
D. so that the two identical machines will pass approximately equal cur¬rents to the load