A shoe retailer decides to record the styles and sizes of shoes that his customers choose. He records this data for an entire year by keeping track of his customers' purchases. Which statement accurately describes the type of data the shoe retailer is collecting?.

The smokey mountains have over 2,100 miles of rushing mountain streams and rivers that flow through the park. in each mile lives a diverse community of native fish, amphibians, insects, and larvae, some of which are found only in the southern appalachians. park managers and scientific researchers test many factors such as fish populations, the watersheds and water tests to determine a) too many lizards are present b) the water quality of the stream c) rainwater is running into local streams d) if visitors to the park are overstaying their welcome