Which one is TRUE about the firm commitment??

If A or B or C is wrong, please explain it why it's wrong. I'd like to understand it.

Thank you so much! :)

In a "firm commitment" A. the investment banker buys the stock from the company and resells the issue to the public. B. the investment banker agrees to help the firm sell the stock at a favorable price. C. the investment banker finds the best marketing arrangement for the investment banking firm. D. B and C. E. A and B