Which statement best describes Cortana?

Cortana is best described as an integrated voice search feature because it functions as a virtual assistant designed to help users perform a variety of tasks through voice commands. This includes searching for information online, setting reminders, and managing schedules, all activated by voice input. Cortana utilizes natural language processing and artificial intelligence to understand and respond to user queries, making it an integral part of the Windows operating system user experience.

The other statements do not accurately capture Cortana's functionality. A command-line interface refers to a text-based user interface, which is quite different from a voice-activated assistant. A file sharing feature usually involves sharing documents or files between users or devices, while Cortana facilitates information retrieval and task management rather than file sharing. Lastly, a system backup utility is a tool used for creating copies of data for recovery, which is not the primary function of Cortana. Thus, the emphasis on voice integration makes the statement regarding Cortana's role as an integrated voice search feature the most accurate.