Which of the Following Statements About Sample Control Is True

Multiple Choice

Which of the following statements about sample control is true?

A) Mailing lists for mail surveys are sometimes unavailable,outdated,or incomplete.
B) It can be difficult to prevent respondents from completing an Internet survey multiple times.
C) It is possible to identify specific user groups within a mail panel and to direct the survey to households with specific characteristics.
D) All of the above statements are true.