Final answer:
A discrete random variable can only take on specific, countable values and the values of P(X) must be greater than or equal to zero. Values of the random variable X can be negative.
Step-by-step explanation:
A discrete random variable is a random variable that can only take on specific, countable values. The values of a discrete random variable are obtained by counting. For a discrete probability distribution, each probability must be between zero and one, inclusive, and the sum of the probabilities must be equal to one. Therefore, statement c is true: values of P(X) must be greater than or equal to zero. Statement d is false: values of the random variable X can be negative if they are within the defined range of the random variable.