A little help with qué vs cuál
When it comes to asking questions, choosing between 'qué' and 'cuál' can be another tricky choice - especially because both of these words can often be translated as 'what?'.
This mini lesson might help to make the choice clearer.
(ps just the linked article above is mine, the pic below is just one off the net for some visual interest)
Great job, Kiwi. Some minor comments:
¿Qué es el arcoiris? is what we would normally say.
You can say ¿Qué libro? or ¿Cuál libro? for your example under Qué. But your explanation is perfect.
Keep up the good work! You are a wealth of information!