The psychologist's conclusion is: "people who are especially overconfident are more likely to attempt to start a business in spite of the enormous odds against success than people who are less confident."
Why? The results of the survey given to 100 entrepreneurs and 100 business managers in order to rate how confident they were showed that the entrepreneurs were much more confident than the business managers.
The conclusion of the argument was clearly made because entrepreneurs are people who organize and operate businesses, and they were the most confident of the survey takers; so those who are the most confident, i.e. the entrepreneurs, are more likely to attempt to start a business.
Answer choice (D) states: "The business managers who were most overconfident were found to have attempted to start businesses in the past."
Thus, if the most confident of the business managers who took the survey also attempted to start businesses in the past, then it strengthens the conclusion that people who are especially overconfident are more likely to attempt to start a business than those who are less confident--since the most overconfident of the survey takers attempted to start businesses.
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