Showing English instead

A reader asking for Lesson 2 Teach Book in Spanish would usually rather have the English one than nothing.

So a read can ask for Spanish and show English where Spanish is missing. content-sdk calls this fallback: when there's no Spanish version to give, it gives the English one instead, marked as English. It never mixes the two: a reader gets the Spanish version of a resource, or the English one.

Try it: compare the two ways of asking in Spanish.

Whether a reader gets English where Spanish is missing is up to how the reader's tools ask, not something you choose as you write. What you decide is whether a Spanish version exists and is published.