Which operating system should be used to develop a mobile app that appeals to the greatest number of users?

Choosing an operating system to develop a mobile app that appeals to the greatest number of users must consider the market share and user base of each platform. Google Android is the most widely used mobile operating system globally, accounting for a significant portion of smartphone users. This broad user base includes a diverse demographic, thus offering developers the potential for greater reach and engagement with their apps.

Android's open-source nature also allows for more flexibility in app development, which can lead to a wider range of applications and customization options. The Google Play Store, which is Android's primary distribution platform, hosts millions of apps and provides a robust ecosystem for developers. This extensive environment further supports the likelihood of an app reaching a larger audience.

In contrast, while iOS has a loyal user base and potentially higher revenue per user due to a generally wealthier demographic, it represents a smaller market share compared to Android. Other options, such as Windows Phone and BlackBerry OS, have much less market presence, making them less viable choices for maximizing user appeal in mobile app development today. Therefore, developing on the Android platform aligns best with the goal of reaching the largest audience possible.