【多选题】[br][/br]Which of the following statements on the preview of a presentation is true? _________
选项：

A:Immediately after the opening, you are expected to give a preview.
B:A preview is a table of contents, an outline of your presentation.
C:Always remember to give an explicit preview before you begin discussing your main points.
D:To specify the topics to be covered is usually a good strategy to give a preview.