Answer:
B) a standby underwriting.
Step-by-step explanation:
This is because, the investment bankers handling the ABC Corporation IPO (Initial Public Offering) listing and selling of shares would have entered into standby underwriting where they made promises to purchase whatever that remain if they were not able to complete the shares selling to the public. Fortunately, it was successful executed hence the reason why they were able to earn a commission of $4 million.