Most apps should only ever render one navigator inside of a React component, and this is usually somewhere near the root component of your app. This is a little bit counter-intuitive at first but it's important for the architecture of React Navigation.
Here's what you might write in your code -- note that this example would be incorrect:
/* In the root component we are rendering the app navigator */
Auth:AuthenticationScreen,// This screen renders a navigator!
Assigning navigationOptions to the wrong component#
In previous version of React Navigation, the library used to dig through your component tree to find navigationOptions. This is no longer the case, and only navigationOptions on screen components of a particular navigator will apply to that navigator. You can read more about this in the Navigation options resolution guide.