Final answer:
The mean age will be 20 years.
Step-by-step explanation:
To find the mean age, we can use the concept of sampling distribution. If the average age of students is 20 years, and we randomly sample 500 students at a time, then the mean age of the sample will also be approximately 20 years. This is because the mean age of the population is representative of the mean age of the samples drawn from that population.
Therefore, the answer is A) 20 years.