Which of the Following Best Defines the Term Standby Underwriting

Which of the following best defines the term standby underwriting?

A) Agreement where the underwriter agrees to purchase the unsubscribed portion of the issue.
B) Amount paid to underwriter participating in standby underwriting agreement.
C) Compensation to the underwriter, determined by the difference between the underwriter's buying price and offering price.
D) A new issue of securities by a firm that has already issued securities in the past.
E) A new equity issue of securities by a company that has previously issued securities to the public.