On the whole, scientists do their most creative work before age forty, a tendency that has been taken to show that aging carries with it a loss of creative capacity. An alternative explanation is that by age forty most scientists have worked in their field for fifteen or more years and that by then they have exhausted the opportunity for creative work in that field. Supporting this explanation is the finding that __. Which of the following most logically completes the passage? ['a disproportionately large number of the scientists who produce highly creative work beyond age forty entered their field at an older age than is common', 'the average age of recipients of scientific research grants is significantly greater than forty', 'many scientists temper their own expectations of what they can achieve in their research work by their belief that their creativity will decline as they age', 'scientists who are older than forty tend to find more satisfaction in other activities, such as teaching and mentoring, than they do in pursuing their own research']