Final answer:
The probability of the complement of an event with a probability of 2/7 is 5/7, which is answer choice D.
Step-by-step explanation:
If the probability of an event is 2/7, the probability of its complement is 1 minus the probability of the event itself. Since probabilities of an event and its complement always sum to 1, we can calculate the complement as follows:
P(Complement) = 1 - P(Event)
P(Complement) = 1 - 2/7
P(Complement) = 7/7 - 2/7
P(Complement) = 5/7
Therefore, the correct answer is D. 5/7.