题目

America’s No.1 health problem? A report published by the American Institute of Stress claims the biggest threat to health today is neither cancer nor AIDS. The report says: “It has been estimated that 75—90 percent of all visits to primary care physicians are for stress related problems.”    It is no exaggeration to say that people today are being attacked by stress. According to the National Consumers League, “Work is the top source of stress for adults who have problems and stress in their lives (39%), followed by family (30%). Other sources include health (10%), concern about 1999年曾报道合成和分离了含高能量的正离子的化合物N5AsF6，下列叙述错误的是(　　） A．共有34个核外电子 B．中氮原子以共用电子对结合 C．化合物N5AsF6中As的化合价为+1 D．化合物N5AsF6中F的化合价为-1