Which of the following statements best defines independent events

a.
two events are independent events if it is impossible for the two events to occur simultaneously.
b.
two events are independent events if the occurrence of one event has no effect on the probability of the other.
c.
two events are independent events if the intersection between the sample spaces of the two events is not empty.
d.
two events are independent events if the union of the sample spaces of the two events is not empty.