单项选择题

若xf"(x)+3x[f’(x)] 2 =1一e -x 且f’(x)=0(x 0 ≠0),则

A.(x 0 ,f(x 0 ))是曲线y=f(x)的拐点.
B.f(x 0 )是f(x)的极小值.
C.f(x 0 )不是f(x)的极值,(x 0 ,f(x 0 ))也不是曲线y=f(x)的拐点.
D.f(x 0 )是f(x)的极大值.