单选题 Virginia, Adrienne, and Dennis have taught history for a combined total of 96 years. If Virginia has taught for 9 more years than Adrienne and for 9 fewer years than Dennis, for how many years has Dennis taught?
【正确答案】 D
【答案解析】[解析] 设Virginia的教龄为x年，则Adrienne的教龄为x-9年，而Dennis的教龄为x+9年，根据题意可得：
x+(x+9)+(x-9)=96→x=32年，所以Dennis的教龄为x+9=41年。