Cuál o qué with "¿ . . . es la precio.?
In the 'Business' module, I leapt in with qué, but got slapped down. How do I know how to choose?
I learned that the difference between "qué" and "cuál" is that "qué?" asks for a definition, so to say "¿Qué es el precio?" would imply that you don't know what "el precio" is. You might get a response like "Well, 'el precio' is how much you have to pay to buy something." Normally, this isn't a question most people would ask, but as a learner of Spanish one might not be surprised if you were inquiring about an unknown vocabulary word. "Cuál" on the other hand, refers to a selection of choices. In the case of prices, it's kind of like asking "Which price - of all the possible prices this item could be - is the price of this item?" We don't really think about it that way in English, but that's how it works in Spanish.
This website has more info on the differences between Qué and Cuál: http://spanish.about.com/cs/grammar/a/que_vs_cual.htm