设f'(cos2x)=sin2x,且f(0)=0,则f(x)等于()

设f'(cos2x)=sin2x,且f(0)=0,则f(x)等于()
A、cosx+(1/2)cos2x
B、cos2x-(1/2)cos4x
C、x+(1/2)x2
D、x-(1/2)x2
【正确答案】:D