Reader’s question: Which of the following is correct and why?

What information do you require?
Which information do you require?

Answer: In the examples you gave, what is open-ended and general and which is more closed and specific, i.e. asking for a choice between a limited number of items. For example:

What information do you require? – I want to know how to register, which form to use etc.
Which information do you require? – I want the information for non-Australian residents, not the information for Australian residents.

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