7.已知函数 (x)=a(e)^2x-(x)^2 有三个零点,则实数a的取值范围是 ()-|||-A. [ 0,dfrac (1)({e)^2}] B. (0,dfrac (1)({e)^2}) C. [ 0,dfrac (4)({e)^2}] D. (0,dfrac (4)({e)^2})