In this sentence, does critical thinking modify questions or does just thinking modify questions?
I answered the critical thinking questions.
In this sentence, does critical thinking modify questions or does just thinking modify questions?
I answered the critical thinking questions.
If critical thinking, as a phrase, is a modifier of questions, it is best hyphenated for clarity: I answered the critical-thinking questions. See Grammar Girl's article about compound modifiers.
As your example stands, one can not know for sure what the author means without context.
It's ambiguous. It can either mean
I answered the critical questions about thinking.
in which case critical and thinking each modify questions independently.
Or it can mean
I answered the questions about critical thinking.
in which case critical modifies thinking, and the noun phrase critical thinking modifies questions.
When speaking, you can disambiguate by inflection. In other cases, context will often solve it -- if you're referring to a test, and it has a section titled "Critical Thinking", it presumably means the second interpretation.
And without context, my intuitition is the second interpretation as well, simply because it seems to be a more likely meaning. Critical thinking is something we test people on, not just thinking, and it's unusual for some questions to be critical while others aren't.