Researchers want to determine which cold remedy is most effective at controlling cold symptoms. They are considering three methods of gathering data: Method A: Researchers give cold remedy A or cold remedy B to people with colds and then observe the duration of the cold symptoms exhibited by each group. Method B: Researchers observe the cold symptoms exhibited by people with colds who choose to take cold remedy A and people with colds who choose to take cold remedy B. Method C: Researchers ask people with colds if they feel better after taking cold remedy A or cold remedy B. Tell whether each method of gathering data is a survey, an observational study, or an experiment. Which option would give the most reliable results?