When preparing a multimedia presentation, you should select one medium or several media that will

When preparing a multimedia presentation, you should select one medium or several media that will enhance and complement presentation elements.

Explanation:

Multimedia presentation is the way of presenting by using the different forms of media and animation. The animation and the media used helps to enhance the specific point which the presenter wants to point respectively. Also, the background music and the sound clips help the audience to analyze the presenter's point of view easily.

in june, we will have been married for eighteen months. (i am assuming this is what you want? the sentence, as you have presented it, is grammatically incorrect--   you want it corrected, yes? )