Random samples are useful because they can represent the entire larger population. They're used often in polls that want to see what the whole country, for example, thinks about something. (It would be pretty hard to ask every single person in the country what they think.) It's important that these samples really are random—if you only asked a question in American high schools, the response wouldn't represent the feelings of all of America, just of high school students and teachers.

Mikaela wants to do a poll of everyone at Martin Luther King High School. Which of these is the best way to get an accurate response?

A
Poll only students in 9th and 11th grades.

B
Poll a random selection of teachers, students and staff.

C
Poll only female teachers and students.

D
Poll only staff who have worked at the school for less than five years.