Let's recall what are the differences between parameter and statistic:
Parameter is a descriptive measure calculated from an entire population of data.
Statistic on the other hand, is a descriptive measure calculated from a sample of data.
Upon saying that,
8,500 is a parameter because it is the entire population. So a survey with 8,500 people is not a statistic, it is a parameter.
On the other hand, 85 is a small sample that you can use for the survey and actually it is just the 1% of the total population and we're confident that this is a statistic, not a parameter.
Therefore, the correct answer is:
D. 8,500