Which of the following best defines a mashup in web development?

A mashup in web development is best defined as a web page that integrates content and scripts from multiple sites. This concept involves combining elements from different sources to create a new application or service that offers more comprehensive functionality or information than the individual components alone. For instance, a mashup might merge Google Maps with local business information, allowing users to see locations and relevant data on a single interface.

The nature of a mashup emphasizes the blending of diverse content types and resources into a cohesive unit, showcasing how different services can interact and enhance user experience. This integration is fundamental to the modern web, where collaboration and content sharing among various platforms are increasingly prevalent.

Other options represent different web-related concepts but do not involve the integration aspect that characterizes mashups. For instance, a site that sells various products does not inherently blend multiple content types or scripts. Similarly, a simple blog platform and a social media profile focus on individual functionalities rather than the amalgamation of various web elements, which is central to the definition of a mashup.