What is the main idea of the second e-mail

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Explanation:

The statement "visual aids summarize main ideas and key points" is true.

Visual aids can be defined as those things that you can look at includin a film, model, map, or slides, to help you understand something or to remember information.

For instance visual aids may be utilized in order to try to combat or prevent a disease by summarizing the key points and factor to take into account about it.