Which of the below is an Android Operating System

Which of the below is an Android Operating System

• Oreo
• Rich Tea
• Custard Cream
• Digestive

EXPLANATION

It contains a number of major features, including notification grouping, picture-in-picture support for video, performance improvements and battery usage optimization, and support for autofillers, Bluetooth 5, system-level integration with VoIP apps, wide color gamuts, and Wi-Fi Aware. Android Oreo also introduces two major platform features: Android Go – a software distribution of the operating system for low-end devices – and support for implementing a hardware abstraction layer. 

  Android "Oreo" is the eighth major release and the 15th version of the Android mobile operating system. It was first released as an alpha quality developer preview in March 2017 and released to the public on August 21, 2017. 

SOURCE

https://en.wikipedia.org/wiki/Android_Oreo