Which of the Following Presentation Situations Is Best Suited for Impromptu

Which of the following presentation situations is best suited for impromptu speaking?

A) In the middle of a staff meeting, your boss tells you to summarize the status of a project you are working on. You didn't intend to make this presentation today.
B) You are scheduled to conduct a workshop for your coworkers on how to use the company's new email system. You have a month to prepare for the workshop.
C) Because of your great success, you have been invited to be the commencement speaker at your former high school's graduation ceremony. The local newspaper will print your address the day after the ceremony.
D) All of the above are suitable.
E) None of the above are suitable.