已知f(x)=∫0xcos4t2dtf(x) = \int_{0}^{x} \cos4t^2dtf(x)=∫0xcos4t2dt,则f′(x)=f'(x) =f′(x)=( ).
(A)cos4x2\cos4x^2cos4x2
(B)2cos4x22\cos4x^22cos4x2
(C)4sinx24\sin x^24sinx2
(D)4cosx24\cos x^24cosx2
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