Select all of the statements that are axioms of probability.

a) the probability of two events occurring is always greater than 0.

b) the probability of an event a is the number of outcomes in a divided by the number of outcomes in the sample space.

c) the probability of an event is a number that is at least 0 and no more than 1.

d) if two events a and b are mutually exclusive (disjoint), then p(a or b)=p(a)+p(b).

e) the combined probability of all possible outcomes is equal to 1.