Final answer:
20 trials are most likely to produce results closest to the actual probability due to the law of large numbers, which indicates that the more trials conducted, the closer the results will approximate theoretical probabilities.
Step-by-step explanation:
The number of simulation trials likely to produce results closest to the actual probability increases with the number of trials conducted. This is because of the law of large numbers, which states that as the number of repetitions of a random event increases, the relative frequency of an outcome tends to converge towards the theoretical probability of that outcome. Therefore, between 10, 5, 20, and 15 trials, option C, which corresponds to 20 trials, would most likely provide the closest results to the actual probability.