Answer:
c) Either A or B or both occur.
Explanation:
Suppose that we have two events
Event A
Event B
We have that:

In which a a happens and b does not and
is the probability that aboth events happen
By the same logic, we have that:

The union of events A and B is:

Which includes either one of them or both.
So the correct answer is:
c) Either A or B or both occur.