In the Libet Et Al

In the Libet et al. study (1983) that asked participants to flex their wrist and record when they decided to flex it,

A) people were not very accurate in determining when they actually moved their wrist.
B) participants flexed their wrists in response to a flashing light.
C) the results suggested that the brain started to flex the wrist before participants were conscious of their decision to do so.
D) researchers concluded there is no free will.