Which of the Following Is an Example of an Unobtrusive

Multiple Choice

Which of the following is an example of an unobtrusive measure?

A) A telephone interview with voters asking them how they intend to vote
B) A three-week laboratory experiment to see whether students who participate in an exercise program lose more weight than those who follow a special diet
C) A mailed questionnaire to mayors asking whether their town has an evacuation plan in case of a nuclear power plant disaster
D) Research on graffiti in a high-income neighbourhood
E) None of the above