Which of the following statements are wrong about the DFT's fast algorithm, FFT _

A、The direct computation of DFT consumes too much calculation quantity, so we need FFT algorithm.;

B、By using the symmetry, periodicity and reducibility of twiddle factor in DFT definition, the calculation process can be simplified and the fast algorithm FFT can be obtained.;

C、FFT is a new transformation based on DFT.;

D、FFT algorithm has many different forms except for that mentioned in our courseware.