问题 选择题 计算(1+1a)÷(1-1a)的结果为( )A.a+1a-1B.a-1a+1C.a2-1a2D.a2a2-1 答案 (1+1a)÷(1-1a)=a+1a÷a-1a=a+1a•aa-1=a+1a-1,故选A.