Which is an example of cloud computing?

A web-based email platform is a clear example of cloud computing as it provides services over the internet rather than relying on local installations or physical hardware. In this model, users can access their email accounts from any device with an internet connection, demonstrating the key characteristic of cloud computing: the ability to utilize resources and applications remotely. These services are typically hosted on multiple servers managed by a third-party provider, enhancing accessibility and scalability while minimizing the need for local storage and processing power.

In contrast, a software package installed on a laptop represents traditional software running locally and is dependent on the individual device's resources. A portable mass storage device is a physical piece of hardware that stores data locally and does not involve any cloud services. Finally, a single web-server, while it may host websites, does not offer the scalability or distributed nature of cloud computing, which usually involves a network of servers working collaboratively to provide services and handle user requests.