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 ______.

• Athe average age of recipients of scientific research grants is significantly greater than forty  
• Ba disproportionately large number of the scientists who produce highly creative work beyond age forty entered their field at an older age than is common  
• Cmany 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  
• Dscientists 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  
• Ethere is a similar diminution of creativity with age in nonscientific fields, such as poetry and musical composition