The probability of the second customer ordering a fish is independent of the first customer.
So, if the events are independent, the probability that the next three customers in a row will order a fish is (P):

Where P1, P2, and P3 are the probabilities of the first, second, and third customer ordering a fish.
Substituting the values:

Answer: The probability is 0.009261 = 0.9261%.
To represent the situation using red marbles:
Given that from 100 customers, 21 prefer fish, it is asked to calculate the probability of 3 customers in a row prefer fish.
From the options, randomly selecting 3 marbles from 21 red marbles and 79 green marbles is the best option, since there are 21 red marbles and a total of 100 (21 + 79) marbles.
Answer: C.