In the Introduction to a Talk,which Three of the Following

In the introduction to a talk,which three of the following are necessary?

A) Focusing the audience's attention on your message.
B) Establishing your credibility.
C) Showing how the topic is important to them,not just to you.
D) Giving a summary of all the points you intend to make.
E) Keeping the audience guessing about the main theme of your talk until near the end,then springing it upon them.