Concept:The correct spelling of the word for "a set of printed questions used to collect information" is "Questionnaire".Explanation:The word has two 'n's and two 'a's in the middle: Q-u-e-s-t-i-o-n-n-a-i-r-e.Option A (Questionnair) is missing the final 'e'.Option B (Questionnare) has incorrect letter order.Option C (Questionaire) has only one 'n' after "Question".Only Option D matches the standard spelling found in dictionaries.Answer:Option D. Questionnaire