Before deciding on a medium to use, which of the following should the presenter do?

A. know the age and size of their audience
B. decide on the number of still or moving images they need
C. compare the strengths and limitations of each medium
D. choose the form they feel most comfortable with

C. compare the strengths and limitations of each medium

Before deciding on the medium to use for a presentation, the presenter should compare the strengths and limitations of each medium to determine which one will be most effective for conveying the intended message to the audience. This means considering factors such as the nature of the content, the audience's expectations and capabilities, venue constraints, available technology, and the goals of the presentation.

Although the other options listed can also influence the decision-making process:

A. Knowing the age and size of the audience is important, but it is more about tailoring the content and approach rather than solely determining the medium.

B. Deciding on the number of still or moving images is part of the content planning process and can follow the choice of medium—or sometimes influence it—but is not the first consideration before choosing the medium.

D. Choosing the form that the presenter feels most comfortable with is also a consideration, but it shouldn't be the sole criterion, as the goal is to effectively reach and engage the audience, not just what is easiest for the presenter.

Comparing the strengths and limitations of each medium (C) helps ensure that the chosen medium will effectively deliver the message to the audience and achieve the desired outcomes for the presentation.