If a speaker says, "Tonight, I'm going to discuss with you two reasons why everyone should recycle, including cost-saving benefits and the problems waste creates in the environment," you recognize this as a(n)

A preview of main ideas.

Explanation:

A preview can be defined as a view to show in advance what is to be shown in the presentation. It is a statement that is said directly to the audience about the main points of the speech.

In the given case, the speaker is previewing his main ideas of the speech by stating the points that he is going to speak. He gave a brief description of his speech that his speech is going to be based on the reasons for recycling, cost-saving benefits, etc.

So, the correct answer is a preview.