To ensure only 'Male' and 'Female' can be selected in the 'Gender' field, what option must be checked?

In a scenario where you want to restrict the entries in a field such as 'Gender' to only specific values—'Male' and 'Female'—the correct option is to check the 'Limit to List' setting. By enabling this option, you effectively create a dropdown list in which users can only select from the predefined values you have specified. This prevents any other entries from being entered, ensuring that the data collected adheres strictly to the designated options.

In contrast, the other options serve different purposes. For instance, 'Show All Values' might display all the data without filtering it, which does not help in limiting the choices. 'Sort Alphabetically' simply organizes the list you provide but does not restrict the choices available. Lastly, 'Display as Checkbox' changes the way options are presented but does not inherently limit the selections to just 'Male' and 'Female', as users could still check or uncheck any other options if they were available. Therefore, checking 'Limit to List' is the method that effectively enforces the desired restriction on the 'Gender' field.