How can you set the duration of a scratch org to 15 days?

To set the duration of a scratch org to 15 days, you would configure this setting in the Scratch Org Definition. The Scratch Org Definition is a key component in Salesforce DX that allows developers to define the parameters for a scratch org, including its duration, features, and edition.

When you specify the duration within the Scratch Org Definition, you can set various characteristics of the scratch org, such as enabling specific Salesforce features or types of user licenses, alongside the period for which the org will be active. This duration determines how long the scratch org will remain valid before it automatically expires. By making the change directly within the Scratch Org Definition, you ensure that the parameters are correctly applied every time a scratch org is created using that definition file.

The other choices do not directly correspond to the process of setting the scratch org duration. For instance, while the Copado DX Mode picklist is relevant to the overall configuration in Copado, it doesn't specifically control the scratch org's duration. Similarly, User Story settings and Account Settings pertain to different aspects of project management and user permissions, not the specifics of scratch org configurations.