The correct answer is D. configuring the SaaS solution. In a Software as a Service (SaaS) model, the service provider is responsible for ensuring high availability, infrastructure management, security, and system maintenance. The customer does not handle backend availability or server-level configuration. Instead, the user’s responsibility is mainly limited to using the application and setting it up according to their needs, such as managing users, preferences, and application settings. Therefore, the underlined statement is incorrect, and replacing it with “configuring the SaaS solution” makes it accurate.