Which of these is an example of a non-random sample?
 A. 
 Out of all the seventh grade students in a public school district, fifteen are chosen to win a trip to a vacation destination.
 B. 
 Airline passengers to Orlando, Florida, are asked about vacation plans.
 C. 
 Registered voters in Arizona are surveyed to determine if they have relatives in Florida.
 D. 
 At a school assembly, five students are randomly chosen to receive free admission to a theme park.