In What Way Was the Phi Phenomenon a Challenge to Wundt's

In what way was the phi phenomenon a challenge to Wundt's system?​

A) ​The phi phenomenon could not be reduced to its basic elements.
B) Specially trained observers proved that the empirical methods used to prove the phi phenomenon were more applicable to their perceptions than that of Wundt's introspective method.
C) ​Although it contradicted Wundt's reductionistic theory,Wundt adequately demonstrated that the phenomenon could be reduced to basic elements.
D) The phi phenomenon demonstrated the existence of consciousness in humans.
E) None of the above.