Select the scenario below that bests demonstrates sampling bias. Select the correct answer below:

Justin wants to estimate the ethnic background distribution of residents of his town. He collects data from 1000 randomly selected town residents by using a random number generator.

To estimate the mean salary of professors at her university, Patricia collects data by recording the salaries of all professors included in 12 randomly selected departments.

Elizabeth wants to estimate the mean height of students at her school. She collects data by selecting a random group of students within her classroom.

To estimate the mean grade point average of students at her school, Annie collects data by recording the grade point average of every 25th student on the list of students after a randomly selected first student.