单项选择题

设f(x)连续可导,且,f(0)为f(x)的极值,则( )

A.当f(0)=0时,f(0)是f(x)的极小值
B.当f(0)=0时,f(0)是f(x)的极大值
C.当f(0)>0时,f(0)是f(x)的极大值
D.当f(0)<0时,f(0)是f(x)的极小值