Research Suggests That Brain Activity Preparing for a Movement Starts

Multiple Choice

Research suggests that brain activity preparing for a movement starts before the conscious decision to make the movement.Which uncertainty is a possible problem with this research?

A) How accurately researchers can measure the time when brain activity starts
B) How accurately people can report the time of a voluntary decision
C) How accurately researchers can measure the time when the movement itself starts
D) How much the results vary between the left hand and the right hand