What are characteristics of app icons for Android apps?

The correct choice highlights the nature of adaptive icons in Android app development. Adaptive icons are designed to provide a more flexible and versatile appearance across different devices and screen sizes. They consist of two separate layers: a foreground layer and a background layer. This structure allows for varying shapes, sizes, and visual effects, depending on the launcher's requirements and the device's specifications. By separating these layers, Android ensures that app icons can maintain their visual integrity and adapt to different display environments, enhancing user experience.

The mention of only needing one icon image for all devices isn't accurate, as Android employs different icon resolutions and formats to cater to various screen densities and sizes. The assertion that icons can only be bitmap images is misleading, as Android supports vector drawables, which are scalable and can offer higher quality without losing resolution. Lastly, stating that vector drawables cannot be scaled or resized goes against their fundamental purpose; they are specifically designed to be resolution-independent and versatile, making them a preferred option for app icons and other graphics in Android applications.