单选题 The ______ of smoking among women, formerly negligible, has grown to such a degree that lung cancer has become the chief causer of cancer-related deaths among women.

【正确答案】 D
【答案解析】incidence发生率，具有影响的程度。ferocious极度的，凶猛的。affluence富裕，富足。impudence轻率，厚颜无耻。