A study at a company found that most meetings showed diminishing returns after 30 minutes, and little could be expected after 60 minutes. Moreover, the most productive meetings were those for which a clear time frame was established. For a meeting at the company to achieve maximum productivity, then, it needs to have a clear time frame and be no more than 30 minutes long. Which one of the following most accurately expresses the conclusion drawn in the argument? ['Most meetings at the company show diminishing returns after 30 minutes, according to a study.', 'In general, a meeting at the company that is no more than 30 minutes long and has a clear time frame will achieve maximum productivity.', 'A meeting at the company will be maximally productive only if it has a clear time frame and lasts no more than 30 minutes.', 'According to a study, meetings at the company were the most productive when they had clear time frames.']