Which of the following statements is true?

a$.$ Return on owners' equity is not an important financial calculation.

b$.$ Financial leverage should not be considered when a firm borrows money.

c$.$ There is no good reason for a firm to borrow money when it has cash to finance expansion.

d$.$ Under the right circumstances, the use of borrowed money can improve a firm's return on owners' equity.

e$.$ The use of borrowed money always reduces a firm's return on owners' equity.