Which of the following operating systems is very lightweight and relies heavily on Internet applications?

Chrome OS is a Linux-based operating system developed by Google, specifically designed for web applications and cloud computing, making it lightweight and highly dependent on internet connectivity for most functionalities. It emphasizes a browser-centric user experience.

Windows is a full-featured desktop operating system that supports a wide range of local applications and can function extensively offline, making it not lightweight or solely reliant on internet applications.

Linux refers to a kernel and many distributions; while some Linux distributions can be lightweight, it's a broad category and not inherently designed heavily on internet applications in the same way Chrome OS is.

Blackberry OS was a mobile operating system, not a desktop OS, and while it had internet capabilities, it was not characterized as 'very lightweight' and 'heavily reliant on Internet applications' in the same context as Chrome OS.