Which of the following operating systems has the largest user base for mobile devices?

Google Android has the largest user base for mobile devices due to its widespread adoption across various manufacturers and devices. The Android operating system is open-source, allowing a diverse range of smartphones and tablets from different brands such as Samsung, Huawei, Xiaomi, and others to be built on it. This flexibility has led to a significant market share globally.

Additionally, the Android ecosystem benefits from the availability of a vast number of apps on the Google Play Store, which further encourages users to choose Android devices. Unlike proprietary systems, Android's accessibility and adaptability to various hardware have made it immensely popular, resulting in billions of active devices in use around the world.

In contrast, while Apple iOS has a loyal customer base, its devices are limited to Apple's hardware, which means a smaller overall user count compared to the variety offered by Android. Other operating systems like Windows and Linux have significantly smaller footprints in the mobile sector, as they predominantly cater to different markets and user needs. Windows, for instance, has almost completely exited the mobile market, and Linux, although used in certain niche devices, does not compete effectively against Android or iOS in general consumer mobile use.