Which of the following was not a signal in Enron’s financial statements of its financial problems?

(a) Receivables increased as a percentage of sales.

(b) Its debt-to-equity ratio decreased over time.

(c) It used death-spiral financing in which it guaranteed that if Enron’s stock fell below certain specific amounts, it would issue more shares or pay cash to SPEs.

(d) All of the above were signals.