Answer is b) Navigator
Navigator is a component that enables navigation between different screens in the applications.
Components are the building blocks for a React Native application. A React Native user interface (UI) is specified by declaring components, possibly nested, and then those components are mapped to the native UI on the targeted platform. There are a number of core components that are commonly used in applications.
When writing in React for the Web, you render normal HTML elements (<div>, <span>, <li>, <ul>, <img> etc.). With React Native, all of these elements are replaced by platform specific React components such as <View>, <Text>, <ListView>, <Image> etc.