Which of the following is not a property of a discrete random variable X, that takes any value from 0, 1, 2,...,n?

1. AFor any possible value of X, P(X = x) ≥ 0
2. BΣ P(X = x) = 1, the summation is taken over all possible values of X
3. CP(X = n) < 0
4. DIf A and B are two disjoint subsets of {0, 1, 2, ...,n} then P(A + B) = P(A) + P(B)