What operating system was developed by Apple specifically for iPhones?

The operating system developed by Apple specifically for iPhones is iOS. Launched in 2007 alongside the first iPhone, iOS is designed to optimize the user experience on mobile devices and is known for its smooth interface, robust security features, and integration with Apple’s ecosystem. This operating system supports a vast range of applications available on the App Store and includes features such as multitasking, notifications, and a focus on touch-based navigation.

The other options represent different operating systems and applications misunderstood in this context. Android is a separate operating system developed by Google, which also powers many mobile devices but is not associated with Apple. Microsoft 365 and Google Workspace are productivity suites consisting of cloud-based applications and services, rather than operating systems, and they do not pertain to mobile device operating systems at all.