阅读下列短文，从每题所给的A.B.C和D项中，选出最佳选项。
“America’s No.1 Health Problem.” So reads the headline of an article published by the American Institute of Stress that claims the biggest threat to health today is neither cancer nor AIDS. The report says: “It has been estimated（估计）that 75 to 90 percent of all visits to primary care physicians are for stress related problems.”
