Answer:
The word or phrase that describes the probability that Arianna will roll a number between 1 and 6 (including 1 and 6) is "certain." The reason for this is that a standard six-sided die always has a number between 1 and 6 on each face, and if the die is fair and unbiased, then the probability of rolling a number between 1 and 6 is 1, or 100%. Therefore, option (b) "certain" is the correct choice.