题目选项分析

Which of the following most logically completes the passage?

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 ______.

【选项】the average age of recipients of scientific research grants is significantly greater than forty