Where do you find the Link button arrow to begin inserting an audio file?

The Link button arrow for inserting an audio file is located in the Insert Ribbon Tab. This tab is specifically designed to provide access to a variety of elements that you can add to your presentation, including images, videos, and audio files. When you're looking to enhance your slides with multimedia elements, the Insert tab is the primary section you'll navigate to.

In this tab, you can find the 'Audio' option which allows you to either upload an audio file from your device or link to an audio file available online. This makes the process straightforward for users who want to enhance their presentations with sound, as all necessary tools are conveniently grouped in the Insert Ribbon Tab.

The other options, though they each serve specific functions within PowerPoint, do not provide the features required for inserting audio files. For instance, the Home Ribbon Tab focuses primarily on general editing and slide layout, the Merging Ribbon Group deals with collaboration and combining content, and the Review Ribbon Tab is aimed at revising and commenting on presentations. Therefore, for inserting audio, the Insert Ribbon Tab is the most suitable and correct choice.