What do you need to select to change the number of slides on the handout to four?

To change the number of slides on a handout to four, selecting the "Slides per page button" is the appropriate action. This feature allows users to specify how many slides they want to display on each page of the handout. By choosing this option, you can adjust the layout and customize it according to your preferences, ensuring that four slides are arranged on a single page for efficient presentation and printing.

The other options do not directly relate to changing the slide count on a handout. The "Colors and styles button" deals primarily with the visual formatting of the presentation, while the "Page setup button" is focused on adjusting overall page dimensions and orientation. The "Handout design button," although relevant to designing the layout of handouts, does not specifically allow you to set the number of slides per page. Therefore, selecting the "Slides per page button" directly addresses the requirement to display four slides on the handout.