Answer:
Users who park at the selected trailheads and cross-country ski lots. ; Convenience sampling
Explanation:
A) The population of interest:
The population of interest should include the concerned individuals which would be those who park at the selected trailheads and cross-country ski lots.
B) By sampling the first 50 users encountered at each fee areas shows that the researcher prioritizes ease or convenience while choosing samples from a population. The first 50 fee users represents the most easily accessible users. Hence, the reason the adopted sampling method is called convenience sampling.