Which of the following is a combination option available for the Sauza Gold Coast Rita?

The combination option available for the Sauza Gold Coast Rita is to add an extra shot of tequila. This choice aligns with the standard practices for enhancing this particular cocktail, as tequila is the primary spirit used in a margarita. Adding an extra shot of tequila provides guests with a stronger version of their drink, which is a popular request among customers looking to enhance their experience.

The other options do not conform to the traditional components of this specific cocktail. Rum and whisky are not typically associated with margaritas, which focus on tequila and lime, while the addition of fruit slices, although they can be a garnish or an option in other drinks, does not represent a standard combination enhancement for the Sauza Gold Coast Rita specifically. Thus, opting for an extra shot of tequila is the most fitting choice for those looking to customize their margarita experience at Outback Steakhouse.