单项选择题

设f(x)在x=n处可导,则|f(x)|在x=a处不可导的充要条件是 ( ).

A.f(A) =0,_f'(A) =0.
B.f'(A) =0,f&#
C.f(A) ≠0,f(A
D.f(A) ≠0,f'(A