Which of the flask is acting as control justify?

In an experiment using flasks to observe a specific reaction, the flask acting as the control is typically the one that does not contain the variable being tested. For example, if the experiment involves adding a catalyst to one flask to observe its effect on reaction rate, the control flask would not contain the catalyst but should have all other conditions identical. This allows for comparison to determine the effect of the variable being tested. Thus, the control flask serves as a baseline to evaluate the results of the experimental flask.