Which ethical consideration is crucial in conducting user studies involving human participants?

Assertion (A): Ackroyd and Hughes's classification of surveys into factual, attitude, and explanatory types is significant for user study methodology beyond merely categorizing data collection tools. Reason (R): The three survey types correspond to fundamentally different research purposes — description, measurement of perception, and theory-testing, respectively — meaning that the choice of survey type determines not only the data collection method but also the epistemological stance and analytical framework of the entire study.

A research method primarily employed in forecasting future events based on the opinion of experts is: